Does anyone have experience with Dicor white lap sealer in a caulking tube. I have a metal roof with a fiberglass cap. Just planning on doing the seams and roof vents etc and not painting the entire roof. I just got this RV a few months ago and can see from the inside that it leaked around all of the vents and seams so I think this is a good plan.

Any suggestions on cleaning and prepping the surface for the sealer? Like lacquer thinner?

Thanks
-Miles