I use a 'pressure washer' to clean mine. I say it like that because it's not your usual pressure washer. This is a unit I bought over 10 years ago that was sold as a home car wash station. It came with the pressure washer, hose reels, vacuum/blow dryer... yada, yada, yada. If anyone remembers Canadian Tire carrying them back then, it was the one that mounted to a wall.
Well, technically it is a pressure washer, but it's pressure output is designed to be low enough to be 'automotive safe'. I've never measured it but I'd guess it's only 20-30 PSI stronger than the 'pressure wash' setting on our garden hose nozzle.
I figure that if it's safe for autos, it's safe for the RV, but that's the only one I'd consider using. I'd be scared to use the father in law's gas beast on this rig, but I do borrow his for the annual spring cleaning of the driveway's concrete.
There's no use crying over spilled milk, unless it's on your keyboard.