My truck was built to be a driver. After two Illinois winters and 18,000 miles, the areas that look best under my truck are the areas that I coated with Duplicolor roll-on bedliner. I only did portions that seemed prone to trouble, like the bottom of the cab, since the stuff is expensive and I wasn't sure if it would work. The bedliner coated areas look so good, that I recently cleaned up more areas(like the underside of the running boards) and applied additional bedliner. The plain ZeroRust areas were rusting and it seems that it doesn't hold up to the grit and gravel thrown up.
The front fenders and the cowl area that is made to rust on an AD is being well protected by the neoprene fender liners I made.
On my next one, I'll epoxy prime everything, then coat the non-show surfaces with the bedliner. It's tough stuff.
http://www.chuckthetruck.homestead.com/Page22.html
