I used a Commercial cleaner. They have mobile units that drive right to the location. I have done it myself, as well,....they do a much better job. I think I paid around 75 dollars total. If you have the hull liner, as I did in my 94, those small black (darkened) spots at rivet locations.....seems to be aluminum particles from chaffing panels.... will not come out. Just clean 'em up and live with it I guess. Polishing is a big project...just read the polishing threads here on the Forums. There is a 34 being polished now and the story is here too.
"If it can't be reduced, reused, repaired, rebuilt, refurbished, refinished, resold, recycled or composted
then it should be restricted, redesigned or removed from production."