I recently washed my TT to remove the dirt from the previous trip.
I did not wash the roof as it gets a thorough rinsing during every hard rain and I do not like to bang a brush against all the pipes, vents and other protrusions that do not leak.
My method is to I rinse a section of the side wall with the garden hose, then scrub it with a long handled sponge mop dipped in bucket with water and dish washing detergent, then rinse the soapy water off and move to the next section of the trailer. Usually the front gets a little extra scrubbing to remove bugs and dirt. Also the tire and wheels get hand scrubbed because of the road grim and crannies to be cleaned.
Then, I repeat the rinsing and scrubbing with Mother’s brand wash and wax solution. There are many wash and wax product and just as many advocates.
The process take a little over and hour for my stick and tin 26 foot TT.