Almost every car I see has those black/grayish scuff marks from shoes and stuff on the vinyl/plastic areas, especially on the doors. I've been wondering for the longest time, is there a way to get those off? Are some of those permanent? I''ve used APC to clean vinyl in some family members cars and I know its working well because I see how the towels turn black when I wipe off the APC, but those scuff marks just stay there and its annoying because sometimes there are so many that it doesn't really look like the plastic/vinyl is clean. So any suggestions on procedures or products out there?