I'm sorry, I probably wasn't clear in my post about the epoxy primer. I usually spray epoxy primer on everything, whether it is bare metal, OEM finish, or whatever. The epoxy primer provides an excellent surface for body filler and other substrates to adhere to.
You should not use the epoxy primer alone as a topcoat however. If when the body work is as good as you want it, apply sealer, and then the paint of your choice. If you are looking for a suede or primer look as the finished paint, then use a single stage paint with some flattener added. Or you might explain to the counterman at the paint store what you are looking to do and he might have some less expensive paint that is designed for trailers, farm implements and such. I did this at a PPG dealer a few years ago and he saved me a bunch of money, but I don't recall what the stuff was called.
Dennis W. Parks
Author of automotive how-to books