A friend of mine told me I should spread seed and then put a half inch of soil over it. I have about half an acre of lawn so this would be a LOT of soil. Is there any way to just spread seed and still have it take without adding soil on top?
Watering is important as is contact with the soil. That's while you'll see folks talk about "rolling" a yard after seeding it - it increases the contact the seed has with the soil. Until that seed begins to grow and establish roots, it'll need to be watered. Obviously you can way overdo this but I've found that it's worked best when I water it well daily. If it is really hot, then maybe twice daily. I don't personally roll my yard but then I live on a farm and seed on a larger scale.
I've heard some folks poo-poo the idea of putting down straw over the seed but it does help to retain some moisture and keep the birds from eating it. Straw - not hay because hay will have seeds in it while straw is less likely to have weed seeds in it - would be what I'd use, particularly if it were hotter. I've generally had pretty good luck as long as the straw isn't too thick and the soil remains moist. Then I just mow it up later on once the grass is well-established. Others will have opinions, I'm sure. You could skip the straw if you are diligent about watering.
A 1/2 inch of soil over a half-acre would be something like 33 yards of soil. A bit pricey and unnecessary.
Yes yes, do not do that. Just spread it and then rake it in with a steel rake. You rake it in more just to hide it from the birds than even for its growth. Grass seed will find the soil if given the right water and sunlight. A half inch of soil over a acre would not be a good use of your time.