So ,excuse me for being frugal but could I use a spray can of epoxy primer over the bare metal for adhesion and then buy a gallon of urethane to spray the whole car,? Hate to buy 2 gallons of primer.
You really want something that is catalyzed (a hardener). You can buy two part paints in aerosols but it's not real common. They have a button on the bottom that punctures and releases hardener into the remaining contents. Here's an example: http://www.spraymax.com/index.php?id=149&L=1