I too would suggest a truck wash for general on-the-road grime.
That being said, herewith a shout out to the campground in Russel, Kansas which allowed me to wash off the diesel oil sprayed all over my TT when my TV blew the oil seal on the high pressure oil line to the turbo. Even though the campground rules forbade washing your rig AND there was a truck wash just across the road, the obvious need to wash that oil off before it damaged the TT, and my lack of a TV to get it to that truck wash, they were kind enough to grant me an exception, and even came down to offer me a bottle of heavy duty degreaser. There are campground owners out there who have hearts and will bend over backwards to help you out, in spite of the horror stories you hear.