Our rear view camera mount has developed a small leak into the upper cabinet over the dining table. Only when we get a heavy rain. I bought a tube of Proflex to do the job but of course the tube will do 100 such jobs so I figured I might as well redo all the penetrations while I'm at it. Outside shower, all lights, 120v and 12v outlets etc. I think the sealant used by ETI dried clear but now all of it is a funky dirty gray. Do I need to remove the old sealant and if so how? Or, would it be ok to just put a layer of new over the old?