Buddy, I saw Charlie on Ammerican Hotrod use epoxy primer and then do the body filer and then prime. I asked on this site and these guys confirmed that epoxy primer was the way to go.
I just got back from the paint store they also confirmed that you should start with epoxy primer. So I invested.
I have a rusty cab that I'm working on and I will be sand blasting the tough areas and DAing the rest then hitting it with the three part epoxy primer, before the fun starts.
Thats my plan.... my 2cents.
Good luck...
