I use this for getting the bugs off the front cap after going down the road.
http://www.pplmotorhomes.com/parts/rv-cleaners/protect-all-rv-wash.htm
I just fill a small bucket, use a telescoping brush, and after a coupe minutes good to go. Obviously it's not "waterless", but rather "rinseless." Nobody has ever said a word about me doing it...and frankly I got the idea after seeing so many MH guys do it. I think the places that ban full on washing are more about stopping the hose down overspray from hitting a neighbor.