I am reinstalling butyl tape, and using dicor on my 2004 Rockwood Freedom 2290. I have scraped all the old stuff off. What is best to use to prep the surface for the butyl tape and the dicor caulk? Soap and water? Denatured alchohol? Mineral spirits? Isoproponal alchohol? paint thinner? Also what is good to use to prep over the old caulk? Where I would be adding to what is already there?