I would be very interested in any more information on this. I'm writing a wiki article on Rust, with information culled from analyzing over 400 forum threads on rust. The Epoxy primer
section contains the following information, which I've seen repeated on the board many times:
Epoxy primer is a two-part mix, with a hardener that has to be added before you spray it. Thus, it's not available in a spray (rattle) can.