How long after using Round Up can I drop KBG seed into the ground?

Technically, immediately. By the time the seed sprouts the Roundup is gone. I'd wait a bit, so if you spot-spray today you can reasonably plant on Saturday, September 1st.

natural crown???? I figure this to mean no shorter than 1.5 inches?

With the watering you're about to give it to get the new seed sprouting, even damaging or destroying the crown isn't fatal. It can regrow from energy stored in the root of the old grass.

Grass crowns sit low, usually immediately above the soil. One inch won't damage them.

but im still going to seed this weekend. Is this OK?

You're tight enough on time that I wouldn't wait, although adjusting chemical balances on a newly-sprouted lawn is a touchy business. The young stuff can't take the beating established grass can.

no more then 1/2 inch

Too deep! 1/4 inch is preferred, 1/8 inch is very good, shallower than that is perfectly workable. Seeds usually don't want to be buried deeper than three times their diameter, and grass seed is small.

Thatch layer (optional I think) or is this recommended?

Do it. You'll be glad you did. Mow afterward with the bag on to pick up the dislodged crud.

not even found Milorganite....I'm I correct?

Either. If you have a Home Depot or Lowe's, they carry it. Seed contains everything it needs for the first few weeks of its life, so you can still use Milorganite. It's available after about seven days, or just about the time your KBG is barely thinking about possibly germinating if it gets around to it. Fourteen to 21 days is more likely on germination.

have a few large bare spots what should I use 3 pounds

Yes. Those bare spots are technically new lawn. If you used two it would work just fine and you won't be unhappy with the final result, however, so don't go nuts.

each day I should collect 1/2 of water in tuna can

Don't drive yourself insane. If the soil surface is damp, it's fine. Synchronize your sprinklers once so you know what you're adding, then just use that timing or modify it by the weather (cloudy? Cool? Still damp? Don't bother watering. Hot, sunny, and dry? Water more).

Thanks for the fast reply and additional information!

Purchase seed here www.pawneebuttesseed.com
I did....purchased 25 pounds of sod quality KBG

Curious to know what you purchased.

Fertilize with starter fertilizer or spread Milorganite 1 week prior to seeding...OPS! guess I'll have to use normal starter fertilizer because I plan to over seed this holiday weekend and have not even found Milorganite....I'm I correct?

Go with the starter fertilizer. Unless you manage your lawn organically, I wouldn't worry about Milorganite at this time. It would warrant additional amendments you won't have to worry about with the starter fert.

Cover new seed with mulch, compost or straw.....I've decided to use compost. However my supplier will not guarantee its weed free. No one around my town will. Is this ok?

You don't really have to worry about weed seeds in compost. Apply a 1/4 inch layer over the seeds.

Water, water, water water......3 times per day first week, 2 times per day 2nd week as necessary until grass is 2-3 inches high.....each day I should collect 1/2 of water in tuna can....

Here is irrigation schedule for new seeds.

water 15-20 minutes twice a day for two weeks
water 20-30 minutes once a day for one week
water 30-45 minutes once a day every other day for one week
water 30-45 minutes once a day twice a week for one week
move into deep irrigation, increasing the time to provide 1 inch of water all over and decreasing the frequency to just once a week.
Starting off, the schedule supplies roughly 1/4 inch of water, then increases that amount while decreasing frequency of application at the same time. Like practically everything that concerns lawn care, this schedule is a general guideline and should be modified to accommodate your specific conditions. The lengths of time should be modified if you have an automatic sprinkler system since that will not take as long to provide adequate moisture. So, decrease amount of water (time) but maintain frequency as is. The tuna cans test is recommended. If it is still especially warm, you may want to irrigate 3 times a day (10-15 minutes if necessary) for that first couple weeks. Your objective is to keep the upper 1 inch of soil moist and not let the seeds dry out.
Baby the grass for the rest of year. Once the seeds begin to sprout, don't walk on it if at all possible.

I ordered midnight and Bedazzled (25 pounds)

Any recommendations for starter fertilizer? Brand and Speedy green setting?

Thanks for the follow-up

Any brand is fine. They will all contain high levels of phosphorus and there will also be postassium, which Milorganite doesn't have.

Just to clarify, Milorganite is a fine fertilizer to use. I am only suggesting you not use it as your starter fert unless organic methods are your preference.

Well I used two bags of Milorganite for $18 vs a bag of Starter fertilizer for $32. My soil already has a good amount of phosphorous in it. So I will let you all know if I get a deep, full, lush, dark KBG lawn using it. I'm thinking that Milorganite is going to be awesome as it is slow release and it takes KBG 21 days to germinate, not to mention we'll probably get a couple of hot days here and there.

Morpheus,
Didn't you use Milorganite?

I got everything accomplished de thatched, over seeded, and covered it all with 1/4 inch of compost in most places.

Watered like crasy last week, but mother nature took over this weekend, in fact I think mother nature might have watered to much..we will see!

Its been a week and 1 day.....is it normal for the KBG mixture to be germinating already? I was under the impression KGB takes 21 days? my mixture is midnight, Bedazzled and Prosperity

Didn't you use Milorganite?

Yes, and alfalfa.

I think mother nature might have watered to much..we will see!

If it wasn't running off you should be just fine!

Its been a week and 1 day.....is it normal for the KBG mixture to be germinating already? I was under the impression KGB takes 21 days? my mixture is midnight, Bedazzled and Prosperity

Yes, that's normal, but it's the first few kernels of corn popping in the popcorn bag. Most likely, the Bedazzled went off first (although I had Midnight II sprouts in 8 days myself). The weather's been very warm, so if you're watering enough the seed is simply a little on the fast side.

Keep watering at your present rate until you're sure there's nothing more sprouting (then add three days).