When home, and doing weekend trips, I wash the motorhome before I leave. When doing our winter "snowbird" runs...either to Florida or Arizona the rig gets really dirty on the way out. While on the road...I simply keep the windshield clean. Most of the time, the windshield washer/wiper is enough. Sometimes not. So, I get on a 3 ft ladder and take care of it.
At my destination...the RV park or cg always has SOMEONE who will clean the RV for a nominal fee. Sometimes a liquid wax is included...sometimes not. I always ask the guy to do the roof, too....maybe 10-15 bucks more.