I wash mine before any long trip. If it is just dusty, I give it a dry wash with Solution dry wash. If it is real dirty then I use my electric power washer and use a little non detergent liquid soap, and power wash it with soft water. Then I put some Blue Coral liquid wax and soap on the power sprayer and spray from top to side, front and back of the coach. I then wipe her down with big beach towels except the roof. I just let the Blue Coral just dry up so that it protects the fiberglass roof. I do not wipe off the excess off the roof.
The paint job on my coach looks as good as the day I bought it ten years ago. Check it out on my profile.