First, start with the front and work back to the ladder! Very important detail. I purchased a similar "coating" from CW! The EDPM roof on my current 5th wheel got cut if I brushed pass a leaf! This stuff coats and protects the roof! Also, I purchased a EDPM "repair kit" with the rubber, cleaner, and adhesive covered the scratches, and put down a piece where the antenna rests! Cleaned, put down "primer" then two coats of the "sealer/coating"! It was around the same price of the OP's treatment, and I think it will go along way to keeping the roof in good condition!
