Up here in MI there is a chain store called Murray's auto parts. I think they're owned by CSK. They sell a line of DupliColor enamels in gallon cans, and they also have "real" wax and grease remover for a low price. Mineral spirits is not going to work.

Aquaintances tell me the DupliColor enamel in conjunction with an enamel hardener (Omni or other) works very well, and also lasts quite a long time. For durability's sake, that is the cheapest paint I would consider using on anything I remotely cared about.

The spray bombs and other stuff don't have any hardener, that's why they take forever to dry (unless you heat/bake them). The lack of hardener also affects durability.