I've not used an aerator to overseed.

But using a powerseeder/slitseeder over the last three years, I've found that I've gotten the best results by setting it at 1/4 of an inch and then using a roller to ensure additional seed to soil contact.

Of course, I ran the seeder several times without laying seed. (Essentially, I used it as an dethatcher set at the deepest setting. Then I seeded at the setting mentioned above)

If you put the seed too deeply into the soil, the young grasslings will not have enough energy to get to the surface.

That's just my two cents.

3-4 inches

Little elite KBG seeds in 3 inch holes is not likely to germinate. KBB should be sowed at a max. depth of 1/2", 1/4 is best.

Thanks all. I got the overseeder today and will use it tomorrow. I hate to get this far and then get poor results by just broadcasting seed. I'll set the overseeder at half the recommended rate and seed in 2 directions. I'll have to experiment with the level of the blades as there's just a lever to control how deep it slices. I'll do a dry run first.

I was answering the aerating depth question.
Are you aerating or slit sleeding?

I was going to just aerate then broadcast seed, but I thought about it and with the slopes of my lawn and the swale out front I went ahead and got an overseeder today when I returned the aerater. I did aerate heavily to maximum depth to loosen very compacted soil. Yes, aerating and slit seeding may be overkill but I got a good deal from the rental place, coupon, etc.

Are you THE Reed Funk?

You have the best of both worlds. The slit seeder will break up your cores for a light topdress. You should still roll the turf afterwards though.

My seeding plans are on hold for now. We got about 2 inches of rain last night. The ground soaked it up well thanks to all the holes in the ground, but it's too wet now to use the slit seeder. How wet is too wet to use a slit seeder? Anyone try to use one in somewhat soggy soil? It would have been a total disaster had I broadcast seed yesterday. It rained cats and dogs last night.
Wow, that would be cool to be getting advice from THE Reed Funk . :)

If the ground is soggy, you will just be stirring up mud. Also the blades slicing up the soil normally propels the unit forward--not so with soggy conditions. With 2", I would think you would need 2 days for it to dry out some. ...lucky you didn't broadcast seed yesterday for sure!