I too have used the Blue beacon - one here in Dallas on I-20 -
well worth it IMHO since I've not washed ANY vehicle other than my Lawn tractor in 10+ years
On my previous rv's didn't have full body paint and
so I just told them to be careful around the decals...
the mgr said, don't worry, we've done a LOT of rv's and are careful -
He also whispered "you wouldn't believe how particular some of these truckers are about their dump trucks and the like"
Still, a cautionary warning is not a bad thing !
one thing I ask them to stay away from with the high pressure is the electronic door lock/handle and the seams...
Again, he said they use brushes around the 'sensitive' areas...
here's a pic I took of one of our previous rigs after going through once - no problems with any of them so far... in fact, the current rig is in dire need of a wash !