I used a product called MacroPoxy a 2 part industrial epoxy to seal of the wheel houses on my project. This stuff is what they use to seal water towers with and seems to have incredible duarability. Goes on via a roller or spray can be thinned, or tinted. You can pick it up at Sherwin Williams.
The flash from the camera throws off how uniform it went on with a roller. How ever i would spray it on for the best finish. It can be topcoated also if you need.
