Hey RJD
Get one of these...
http://www.littlegiantladder.com/lit...ork-plank.html
I got mine just before our trip to Disneyland. The workplank is very sturdy on the littlegiant ladder. It was a breeze washing the top of my trailer.
While we were at the RV park near Disneyland a self contained cleaning truck drove up to wash and detail one of the other rvs at the park. I wish I had the name to pass on to you...I'm sure you can google "cleaning truck" and find them.