Butyl tape

I used a gasket scraper to remove what was possible, most of the dried-out stuff will scrape from most of the surfaces easily. Extra care needs to be taken though on the painted aluminum surfaces, like siding,  for all the obvious reasons. The really hard stuff that won't scrape without the possibility of causing some kind of damage dissolves easily using a rag and paint thinner. A bit of rubbing takes it most of the way off without a lot of elbow grease. Then just to be sure it is clean for the next application, I waited till it was dry and then took a clean rag and some denatured alcohol to it. The alcohol will clean the surfaces completely of grease, wax, and putty. ( It will dissolve the putty, but it is a much more difficult process to use the alcohol instead of the paint thinner.)  Once both mating surfaces are cleaned, the new putty should not have a bit of trouble sticking solidly to your fingers and giving you fits, because you know that the application should be easy at this point....at least, that was my experience...