Later that night, after removing the rest of the flooring, heaters, and upper side panels, we decided to go ahead and give Chitty Bang a good Scrub Down so we could tell where the dirt ended and the rust began. We blew it out with our leaf blower, bought a big work light and some scrubbing brushes (broom with hard bristles and a handheld hard bristle brush), made a soapy bucket with Dawn Dish Soap, and went to town.
We kept our big workshop fan blowing to help dry it faster, and we would clean in sections and then wash down with the hose. Crab used our broom with the squeegee on it to help move the water out of the back of the bus. After just a couple of hours, Chitty Bang was as good as new, and we had a better idea of where our Rust was.