If you do any new seeding now, you will have 100% crabgrass in just a few short weeks. So don't do it now!! The time to reseed cool season turf is in the fall. That might be late August to early Sept for you. Until then I suggest you practice the best lawn care you can. Even weeds look better than nothing when they are well watered, mowed, and fertilized. Get into the habit of watering deeply and infrequently. Deeply means 1 inch of water all at one time. Infrequently means once per week when temps are in the 90s and once every other week in the 80s. Measure 1 inch by setting out empty cat food or tuna cans. Time how long it takes your sprinkler to fill the cans. That is the time you will use from now on every time you water. If your soil will not accept all that water at one time without runoff, either change to an oscillator type sprinkler or do something to soften your soil. Shampoo is what I used. I'll tell you more if you want more on that. By watering like this you will seriously affect the ability of new weed seeds to germinate. They need frequent/daily water. Mulch mow your grass at the highest or next to highest setting on the mower. Tall grass helps to prevent weeds and also grows deep, drought resistant, roots. Fertilize with chemicals about now for the first time this year. If you use organics, then you could have fertilized earlier. Don't think in terms of plowing. Think in terms of scraping. If you have the resources to do a full renovation, then hire a landscaper with a tractor and box blade to resurface your lot. It should take about an hour. If he has the wrong equipment it might take a week. You're paying by the hour so make sure it is a box blade on the back of a real tractor and not a Bobcat or Skid Steer. Most people who write in here about weed n feed are unhappy with it. A better alternative is to apply fertilizer and then follow up in 2 weeks by spot spraying any remaining weeds. Some weeds will go away simply from being fertilized, some will go away when the grass becomes healthier, and some will go away when the grass is taller and more dense. Just spray the remaining weeds. In full sun your grass seed mix should contain some Kentucky bluegrass. At least in my opinion. It spreads to fill in thin spots helping to keep weeds out even if they do sprout.

There are two kinds of sedge you need to be concerned about. Nutsedge (nut grass) is one of them. It is a swamp type plant that practically requires continual moisture. Deprive it of continual moisture and it seems to go away by itself. I've had several infestations following some calamity in my lawn. I've done nothing and it goes away. The only thing I can think of is the lack of water from my infrequent watering habit. I've seen nutsedge growing on a high spot in a river. Once your grass is in and you go to deep, infrequent watering, the nutgrass may go away. Give it until next June and then do something about it. The other sedge is green kyllinga. It looks just like nutsedge until it goes to seed. Green kyllinga will grow in very dry soil. My neighbors have some on a side of their house which has not received any water in 20 years other than rain. While it can stand the dry soil, it is only growing up against their house on the west side, so possibly it cannot stand a full day of sun.

Whenever I've done overseeding, I had the lawn core aerated first. Much of the seed falls in the holes. These seeds will require much less watering since the water accumulates in the holes, they get wet and they don't dry out very easily. In this case, I rarely watered. Only if we went a week or so without rain. Maybe if we had 4 sunny days of temps in the 80's I would water also.

@Jim Mac: Thanks for the pics. Let me give you some tough love. You say your lawn does not look bad but I can tell you it has serious problems. I don't see many lesions but that thick matted brown area is a symptom of fungal diseases like summer patch. It is caused by too much water and heat. You said you water a lot but "still" have burned patches. Those patches are not from drying out. It may well be from over watering. If you are in NJ when did you find a dry day to water the lawn? I'm in northern NJ and we've had buckets of rain about every few days for much of the summer. What exactly is your watering schedule. You have an irrigation system? Have you ever measured how much water your are putting down with tuna cans, or by reading the water meter? I'm curious about the $200 water bill. I pay 0.55 cents per gallon for water and I have to think you can't be far off from that. In your photo plus maybe the shaded area you might have 1000 sf??? If you watered one inch of water that would cost about $3.50 per watering. If you watered every week for 13 straight weeks that amounts to under $50 for the entire summer. Either your pool is using more water than you think or you are far over watering your lawn. Maybe you could provide more feedback on that before we go any further. Here are two sections of my lawn from today. One is KBG sod and the other is a standard landscaper's mix of rye, fescue and KBG, which is probably what you have. You can see that they look almost the same. My point is that the mix of grass can be a good thing and it looks very nice when healthy.