Another trick that I use is that I use the small MF's (12 x 12) from Target, either Vroom or Viking brand, as the washing media instead of a sponge or mitt. This way I can just throw 12 or so into the bucket and use one fresh towel per panel and keep the ONR solution clean. This solves any problems with the wash media not rinsing clean and causing marring. This along with a pre-soaking panels has kept wash induced marring to a minimum on my black C6 vette and black Honda, two nightmare cars.