The soil where I'm planting is hard. A cultipacker or just letting rain bury the seeds doesn't work because of how hard the soil is. Should I set my tiller where it barely breaks the ground to try to bury the seed, or do you think it would bury the seed to deep to germinate?

What kind of seeds are you planting? Would a disk or drag work? Soil crusting can seriously inhibit seedling emergence. A light disking at/after planting would help to break up a soil with a hard crust, and improve emergence if your soil is that hard.

If its that hard - you should roll it over with a moldboard plow - or a subsoiler can break up what sounds like hard pan.

You'll never get good root establishment with a light disking.

I've seen hardpan so hard that a plow bounces on top - Comes from working the upper 1-6" of soil with heavy machinery usually. If you can only overseed - Rye is one of the few seedlings that can help break up hardpan.

If its just dry and sod-filled - thats a whole other story.

Can you roto-till 4-6 inches deep? Do it if you can. Otherwise, try to find a used 2-bottom or 1-bottom (depending on your tractors ponies) plow to work the ground.

bottom plow then harrow it works gaurenteed

I read this as a soil crusting problem (top of soil gets hard after working/planting). I completely agree with subsoiling/plowing if it is the whole plow layer (top 6-8 inches).