I usually just wash mine with a mild detergent (dish soap) and then 303. I am not worried about black marks. But, it is an Aire, and for the first time since buying it about three years ago I opened the floor and cleaned out the sand last weekend. It is a regular floor and I was surprised how much sand had actually accumulated. No wonder my floor was going soft. The grit had gotten in the PRV. Washed out the sand and took a Qtip to the valve - now the floor is holding air much better. I don't think I would ever skip the floor clean out again.