Matt at SOTAR has recommended that we use MEK as a surface cleaner. I wouldn't use any other solvent on a Sotar unless recommended by Sotar. Mild detergent and water for any dirt/grit, and then MEK for scuffs and other things that won't come off with soap and water. Used plenty of MEK- once the rag starts feeling sticky, it's time for more chemicals. That said, we have stains on the bottoms of the boats the origins of which I can't figure out. I can't get 'em off.
Shoot me some pics and I'll take a look.