You can get yourself a pretty cheap spray gun and automotive primer at most body shops. Probably wouldn't run you more than 50-60 bucks total. Depends entirely on how good of a job you want to do. You could always just go nuts with several cans of automotive spray primer you can buy at Walmart. Just remember, primer is a flat color and you'll need to cover it up with a real paint to properly seal it - if you even care.