For 7 years I have been using camco RV wash/wax and it leaves a great shine. My only recommendation is to use a SOFT brush. I have used a stiffer brush to get the bugs off and it has dulled the front of the trailer and taken its toll on decals (I assume small scratches from the stiffer bristle brush have taken away the gloss). I use Camco black streak remover to take care of any stubborn stains.
One quick note on black streaks--They are caused by the roof/gutters being dirty so minimum annual cleaning is recommended. I just use the camco RV soap and a brush. Also, black streaks let go too long will be come permanent. I have seen this on two aluminum trailers.
I am experimenting with using a foam cannon. This device fits on the power washer and COATs the RV in a thick soap film like at the car wash. The theory is that the thick/soapy film will loosen the dirt/bugs enough so that a soft bristle brush or even better a microfiber mop head can effectively clean the RV.
Products I mentioned below:
Microfiber wash pad
Camco RV Wash/Wax
Foam Cannon