Can't use a conventional paint gun, the bedliner material is too thick. You can also buy it (locally at Car Quest) that you just shake it up well and apply it with a small roller, dabbing the hard to reach places with a brush.

Plain old Rustoleum works well. I've also found that Ace Hardware has their own rust resistant coating in both flat and semi-gloss black in quart cans, only about $7.00. Around here we call it poor man's Por-15.

Hotrod396, excellent job on the firewall and the bottom, looks great and should be extremely durable, too.!!!!!!