Originally Posted by easy sawyer
Apparently the spots are the aluminum dust created as the trailer skin flexes against the rivets. So the usual carpet cleaners would only spread the black through the covering fibers, making matters worse.
Exactly right, the aluminum dust is the culprit, so Shari's suggestion of a vacuum cleaner does not work. The solution I describe in the link above does work because the paint makes the backing of the fuzzy wall covering impermeable to the dust, so the spot does not reappear.