filon help

We painted our teardrop with a 2 part epoxy paint. It actually turned out nice. The paint actually looked like aluminum! The problem came in when Jason (my husband) pulled it to our friends house 50 miles away to build cabinets to put in it. He didn't brace the inside,(by the hatch) so the back and forth motion worked the screws lose. They started coming thru the paint, caused cracks in the paint, then we got water damage. It was barley noticeable at first. By this spring it was starting to get bad. So we bought filon. My question is, do we need to sand the paint off? Can we just put the filon over the top of it? And we had to replace a section of the outside, should we put luan over the plywood, or can we just put the filon over the ply? Should we float the filon or use an adhesive? Any help will be appreciated.