A Few years ago I Painted my Willy's Jeep Frame with Van Sickle Paint from Orscheins. It's tough stuff and they sell matching hardener to go with it. They have two versions of their paint. Have also used it on a boat trailer with a brush without hardener. If you go with the Rustoleum, use the "Professional" version in the gray labeled gallon cans and it can be brushed or sprayed. You can email the company any they will let you know what kind of hardener to use. I believe its oil based similar to PPG ALK-200, but I could be wrong. I brush painted my pop-up camper frame with it and it worked out well. I have not used POR-15 but I have heard good things. I haven't seen anything painted with Por-15 over a few years ago so I don't know about real durability. Good Luck
