I've been using a foam cannon with the "ceramic" wax mixed in with the soap and it does a pretty good job on the trailer. Originally got it for the cars and it does a great job on them too so figured I'd try it on the trailer.
Makes washing so much easier. Just spray it on, use the washing brush to wash it then rinse it off. No more buckets to fill/haul around.
Setting up the pressure washer is about the only thing that takes time, but I've got the quick connect hose fittings on it, so not a big deal.
Mitch