3alarmer 

...if I could afford it, I'd use an epoxy primer. As it stands, I've been using a self etching primer in Rustoleum cans. It goes on grey, then a coat of white primer over that, within the recoat window. For the color effects I mostly try, I need a white base primer, although some of the darker stuff in metallic looks OK over the grey. The color coats come from a wide variety of sources. If I can get an exact match for what I want from House of Kolor, I buy some of that in a small enough quantity to do a frame. fork. I've also used various brands of color enamel (from Rustoleum and Krylon, for example) as my color coat.

I've even experimented with Testor's enamels, in the msmall spray cans from hobby shops, but by the time you buy two or three of those cans, you're almost at a price point where custom mixed from the auto paints store is a better choice. That Follis has self etching primer, then white primer, then a silver metallic, then a transparent red enamel, then decals, then Spraymax 2K clear Glamour over everything.

There are certain colors that you get by varying your primer color, like Rauler blue is accomplished by using the same blue colorcoat as Colnago, but over a rust red primer.