If you are going to sand it to bare metal you will need a self etching primer. You can get it in a spray bomb. How do you plan to apply the paint? If you have dents you can fix them with body filler (bondo) .You can get custom mixed colors in spray can's ,but it's about 23.00 a can. If you can buy your paint by the pint or quart you will save money.Paint is like most things , you get what you pay for. So if you plan on making it hold up , spend a few extra bucks and get good paint.