Hi gle2011

I will let others chime in as I had a similar question last year but what I got out of it is dormant seeding works well for bare patches but if you have to overseed a large area or a lot of large bare spots fall overseeding would be better.

I have done both. Did some dormant seeding on a few dead spots from a fungus attack last fall. By spring all those spots had filled in great so definitely worked. I don't know how successful it would have been if it were a much larger project.

When is the best time? Well, that can depend on the zone and the weather patterns but generally one can seed a lawn when cooler weather is almost upon us. This can usually mean from August to October. Remember, seeding later in fall results in growth without competing weeds.
If the seed makes good contact with the soil then you need not worry about whether you should or how often you mow your lawn; the seed shouldn't be bothered by the whirring blade.
Topping seed with topsoil or compost can allay fears of its being lifted and scattered where you don't want it.
After seeding raking can be done to put it in better contact with the soil....or using a roller will do fine.
Sprinkling with the hose will also send the seed down more for better soil contact.
Further sprinkling will keep it there and promote germination. Don't flood your lawn...too much is too much...seed doesn't need a bath...just a shower.

Whether you choose to put down a "starter" fertilizer is up to you...experts usually do recommend....but it could be just another attempt to sell more fertilizer.
If you do fertilzie, be sure to water it in. Fertilizer can be done around Labor Day and again at Thanksgiving.

As your normal grass grows, it can be mowed at its normal height.
Many 'experts' suggest you mow lower than normal to allow more moisture to gain entry to soil but I don't agree---this just opens the soil to drying out if there is still lots of summer left in the calendar.

Just in case your lawn shows a lot of weeds, take care of that first....you cant put down seed if you intend to spray a herbicide. That would kill the seed.