I heard you can add Marine Clean to the water so that the surface is oil free and ready to paint.
The sand and paint residue can be cleaned up pretty easily with planning and prep ahead of time (Plastic tarps and settling basins?).
Water under paint may or may not be an issue. If I got a hold off one of these systems there would not be any paint left on my car for water to get under. Did you see how easy they blow through paint!
Does anyone have any experience with them? All I can find is marketing BS.