RE: window molding "black spots"
I've had good luck using an SOS pad, scrubbing lightly so as not to chew up the rubber. When I bought my trailer, it was sitting for a few years and the moldings were pretty bad in spots now, just washing it a couple of times a year seems to keep the problem in check. Some of the new trailers I've looked at have are using black moldings instead of white which seems like a good idea to me.