Wait, slow down!

I would start with scalping and see if you need to dethatch. A reel mower can scalp it very low if the lumps don't stall the mower. You might need to rent a powered reel or rotary mower to take it down the first time. Take it down to 1.5 inches first and see what you have. That will probably cut off all the green leaves and leave you with brown stubbs. At least you'll be able to see the soil and evaluate any remaining thatch.

Topdressing will add exactly zero nutrient value. If you are worried about soil health and nutrient value, then apply an organic fertilizer like alfalfa pellets (rabbit chow). Since you're in HI, it might be easier to get something else rather than alfalfa. Ground mung beans??? Visit your local feed store - preferably one serving ranches nearby. Any ground up nut, bean, or seed makes an excellent organic fertilizer and will improve your soil better than anything else you can use. If you can find a poultry litter based organic fertilizer, that would help revitalize the soil. I used to use ground corn meal, but it got too expensive last year. I switched to alfalfa pellets and am very happy. The cost of these raw materials in a plain paper bag is about 1/5 the cost of commercially bagged organic fertilizers. In fact I have just the photo for you.

This image is from mrmumbles a few summers ago. It is a zoysia lawn that had not been fertilized that year. He applied alfalfa pellets in mid May and took this picture in mid June.

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This makes it easy to see how well the organic approach works. Color is improved, density is improved, and growth is improved. Again, any ground up nut, bean, or seed works. Even used coffee grounds make a passable organic fertilizer. What will not work is ground up fruits or leaves. Toss those into the compost bin.

Beyond that, delay any topdressing for the sake of leveling it out until you have read up on the topic of leveling. Search this forum for leveling bermuda lawns. Do you want to have the best lawn on the block?

The dead spots will likely come back unless they are in the shade. My experience with zoysia is that all of last years issues disappear when the sod awakens in the spring. But in HI you might not have spring?? Is the lawn green and growing all year long? If shade is an issue, there are some fine bladed varieties of zoysia that do well in the shade. Emerald is not one of them.

Can you post a picture of the lawn? If possible take the picture in the shade or on a cloudy day to reduce the contrast.

How often were the previous owners watering? Do you have a system? I suspect they were watering too frequently and not long enough, but would like to see your reply to that.

You can use organic fertilizer any time of year. Chemical fertilizers should not be used in summer heat and drought. The salty chemicals add too much extra stress to the plant.

As dchall was posting this I was out breaking my back in the hot sun working on the lawn so I didn't get the chance to incorporate the advice. I'll update with what I did and we can all hopefully learn a little:).

My lawn was many years neglected. We ran the dethatched over it twice at 90 degree angles, rakes that all up and then did it again. The section I'm working on is about 2000 sq ft and we pulled up over 30 large trash bags worth of thatch. The exposed grass was now 3-5 ". I took it down as low as I could with a rotary mower then went at it at the highest setting on my reel mower (mclane3.5 hp, 10 blade). It had a hard time getting through the grass and it was very slow going. Got it down to about 1.25-1.5". Next morning I realize there is still a thatch layer down there. Had the dethatcher come back out and hit it again. This pulled up 80% thatch but some soil as well. ( my soil is essentially beach sand). This was very fine thatch so I had to work really hard with the rake to get it up. Very labor intensive. Got several hundred pounds more. At this point I ran over it again with the mclane on the highest setting to catch any stragglers. Then I ran some organic compost through a 1/4" wire screen I made - didn't want any chunks in there to mess with the mower later- and put a very fine layer on the lawn, probably about 1/8" with more in some low spots. Finally I added about 2-3 pounds of 16-4-4 fertilizer and have been watering twice/day.

Two pictures are lawn in midst of first dethatch and after final dethatch. The secon picture is half raked and half unraked.

Dshall- lawn has been essentially ignored for several years. No sprinkler system. And yes, I want the best lawn on the block:). Well, maybe second best. My 93 year old neighbor keeps her yard immaculate. I'll never beat her!

I'm a complete novice so bring on the critiques. I still have another section of yard to do later.

Couple questions at this point:

- the grass now is really thick, almost woody. Is this a problem that will just go away as it starts to fill in?

- eventually I want it very short. Should I buzz it down low now or wait until it is more healthy? I am on 3rd highest setting of 4 on my mower. It since the pieces are so thick it's having to work hard to get through it.

After third round of dethatching.

As it stands today.

Many here are shoveling snow, so you don't get sympathy points for commenting on the hot sun ;0

I'll take a neglected lawn over a hyper fertilized lawn any time. At least you don't have a salty soil to deal with.

Since you are new to this,...

Basics of Lawn Care

After reading numerous books and magazines on lawn care, caring for lawns at seven houses in my life, and reading numerous forums where real people write in to discuss their successes and failures, I have decided to side with the real people and dispense with the book and magazine authors. I don't know what star their planet rotates around but it's not mine. With that in mind, here is the collected wisdom of the Internet savvy homeowners and lawn care professionals summarized in a few words. If you follow the advice here you will have conquered at least 50% of all lawn problems. Once you have these three elements mastered, then you can worry about weeds (if you have any), dog spots, and striping your lawn. But if you are not doing these three things, they will be the first three things suggested for you to correct.

Watering
Water deeply and infrequently. Deeply means at least an inch in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. Do not spread this out and water for 10 minutes every day. If your grass looks dry before the month/week is up, water longer next time. If that does not work, then you might have to water more than once per week during the summer's hottest period. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds.

You will have to learn to judge when to water your own lawn. If you live in El Paso your watering will be different than if you live in Vermont. Adjust your watering to your type of grass, temperature, humidity, wind, and soil type. It is worth noting that this technique is used successfully by professionals in Phoenix, so...just sayin.' The other factors make a difference. If you normally water 1 inch per week and you get 1/2 inch of rain, then adjust and water only 1/2 inch that week.

Mowing
Every week mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. However, bermuda, centipede, and bent grasses will become the most dense when they are mowed at the lowest setting on your mower. In fact there are special mowers that can mow these grasses down to 1/16 inch. Dense grass shades out weeds, keeps the soil cooler, and uses less water than thin grass. Tall grass can feed the deep roots you developed in #1 above. Tall grass does not grow faster than short grass nor does it look shaggy sooner. Once all your grass is at the same height, tall grass just looks plush.

Fertilizing
Fertilize regularly. I fertilize 5 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above. Follow the directions on the bag and do not overdo it. Too much is better than too little*.

At this point you do not have to worry about weed and feed products - remember at this point you are just trying to grow grass, not perfect it. Besides once you are doing these three things correctly, your weed problems should go away without herbicide.