Remove Dirt Stains?
I suspect that what you are seeing is actually more than just dirt or stains. What I suspect that you are seeing is more likely corrossion, oxidation, or "tarnish". The constant contact with the awning fabric (and the moisture that it may have trapped next to the skin) likely abraded away all of the plasticoat which opened the road for oxidation to begin - - this was a problem with my Overlander when the original A & E Travel Awn 5000 was removed three years ago. If what you are seeing is oxidation, then polishing is about all that will remove the discoloration - - the question becomes one of which will be more obvious - - the current oxidation or polishing to remove the oxidation that might create a brighter/glossier finish than that of the surrounding skin.
Kevin D. Allen
WBCCI (Lifetime Member)/VAC/Free Wheelers #6359
1964 Overlander International/1999 GMC K2500 Suburban (7400 VORTEC/4.11 Differentials)
1978 Argosy Minuet 6.0 Metre/1975 Cadillac Eldorado Convertible (8.2 Liter V8/2.70 Final Drive)