Blue Beacon! There are also some local RV/Truck wash places that do an excellent job as well as long as you don't mind paying the money. We are currently in Yuma, AZ and we will visit the local RV wash facility that does a great wash job for $1.50/ft or $2.50/ft if you want them to add a spray wax to the exterior (not great but better than nothing).
One way or another you, or someone, are going to need to get plenty of water, soap, brushes and some towels to touch the sides of your RV. Adding a good wax job after all of this happens is also a very good idea but is quite expensive if you are not willing to do it yourself.