The primer I am using is a Waterborne 1 part Polyurethane primer sealer. It's non self etching & requires a separate Etch step before spraying. Check out their products at Aircraft Finishing Systems In talking with Paul (the owner of AFS) he said that the epoxy was a great primer... The definition of "primer" is a substrate to hold the surface paint onto the metal. It is very porous so that the top coat bonds good to it. The primer sealer has a bit of poly top coat mixed into it so it gets just a bit more of a shine (not much) and seals the surface to moisture penetration and other contamination. Also it's so easy as you have just 1 part to use.

Paul also does not recommend "self etching" primers as they don't give an even etch in all cases. So the procedure is as follows...

Clean parts with lacquer thinner (removes blue ink, sharpie, etc) (use MASK)
Wash with dawn to remove oils etc.
Etch aluminum with AFS Cleaner / Etch (acid product) ps, put rubber gloves on at this point. (use MASK)
wash with clean water, dry.
Paint with primer sealer.

It dries to touch in about 5 min. However it takes about 24 hours to harden. If you start handling it before then the primer will scratch easily. After 24 hours it is hard as nails.

All water based so cleanup is a breeze. If anything sticks you can always strip it off with lacquer thinner before it sets fully.

That's what I know. It's great stuff, try it!

Primer Wars is an in depth article I wrote for our local EAA chapter newsletter about my learning through this process...