http://southernpolyurethanes.com/Produc ... primer.jpg
The epoxy primer that I mentioned has etching properties in it, and yes it is the way to go with anything bare metal, I have shot it over aluminum, sanded chrome, steel, galvanized crap, with very good results.
Etch primer is basically nothing more than lacquer primer with some acid added to it, it is not catalyzed and much weaker than epoxy primer, the only reason to use it is in high production work because of its fast dry times.
If you go the epoxy route and he uses basecoat/clearcoat, make sure he activates the base with whatever clearcoat hardener for maximum paint adhesion and durability, as little as 5% clearcoat activator in the color makes a great difference in the end.
Feel free to PM me if you need additional info.