Kleen Strip Aircraft Remover (stupid name, great product). Follow the directions, and try NOT to breathe in the vapors (major stink). Rinses with water. Clean off ALL the stripper (lacquer thinner works well for this, too). Then sand (180 to 220 grit) to give your metal some tooth.
I don't recommend Krylon or Rustoleum paint only because they are oil-based, and will make a wrinkly mess if you use anything BUT those products later on. So if you decided to use a clearcoat on it, a lacquer or urethane clear would wrinkle and soften the Rustoleumylon.
Don't know much about Montana paints, but I've heard good things.
Lacquer primers (DupliColor, etc) dry quickly, sand nicely, not terribly durable.
Epoxy primers (like US Chem's SprayMax cans) are wonderful, but only good for a few days once activated. Epoxy gives the best protection against corrosion on bare metal (etching primers contains slight amounts of acid that can cause problems later on)