Great thread!
I've used MM Gray Primer out of the rattle can just because that's what I started with. I tried a Rustoleum primer, thinking it would be similar to Don's results, but it took that stuff a month to cure and I ended up putting fingerprints in it. I also tried Tamiya's white primer, but really wasn't impressed with it either.
I do want to try a bottled primer for airbrush use, but I've looked around and no one seems to carry it around here. Can anyone recommend an online source for Mr. Surfacer? I've been wanting to try that for ages.