On a rig that hasn't seen cleaning for a long time I would leave the pressure washer in your garage and prepare for a more thorough wash with a brush on your hose. As mentioned above too much pressure in the wrong area will do damage to decals, seals etc. Get some good soap in a bucket, some black streak remover and go at it. The roof manufacturers have recommended products based on the material on your roof. I have used simple green with good results...just please take care up there and take notice of any seams needing dicor. Some 303 aerospace protectant on tires and decals will really protect them well. I just don't think there are many shortcuts to the labor involved unless you pay others to do the work for you.
Daryll
