I have to admit, I've only done it a couple times, because it's a LOT of hard work. This time, I got a brush that extends and connects to the garden hose. There's a reservoir for car wash liquid at the brush, and a selector knob to choose between rinse and soap. It cost about $20 at Target.
It's still pretty difficult to do, but it's nice to be able to scrub some of the ground-in dirt off the fiberglass. The brush is okay - I had a couple problems with the hose loosening (there's no swivel to let the hose spin around, so as you're moving around it'll tend to loosen the connection to the garden hose) and the knob popping out when I didn't put it back in correctly, but the results are definitely better than I'd gotten from other solutions (for example, the Mr. Clean Car Wash set).
The camper definitely looks better... guess the trouble was worth it.
