[Don Ro]

Wait at least ten days to two weeks before you plan to sow grass seed.
Broadleaf weeds should start to turn brown in three or four days and be completely dead by the end of the 10 day wait. The herbicide will have begun to break down after ten days, so new grass seedlings will not be harmed.
To be extra safe, water the area judiciously at the end of your waiting period to leach the weed agent down past existing roots.

Broadcast "starter fertilizer" at half the suggested rate prior to seeding, then half the rate after seeding. That's what I do, but nothing un-American about following instructions on seed package.
Depending on ambient temps, generally, on flat earth, water 10 min's twice daily...out here, I would water at ~ 10 a.m. and at ~ 2 p.m. YMMV.
Check your soil...too much water will kill the seed.

Overseeding rates for lawn turf should range minimally from five to ten pounds of seed per 1000 square feet.
Double that if the turf is expected to withstand much traffic.

Let new seedlings get to be ~ 4" tall prior to mowing.
Don't water the night before and the day you intend to mow...and mow w/super sharp blade!

I've never heard of freezing seed.

Enjoy your new turf.
.
Edit: "...following instructions on seed package."

Make that: ...following instructions on fertilizer package.