Pressure test camper for leaks

I am guessing they have a large blower unit with an adaptor for a window. The blower comes on and fills the camper with air from outside. It doesn't blow up the camper (like a ballon) but it will pressurize it and while the blower is running, someone will take a sprayer bottle with dish detergent and they are spraying all the door frames, window frames, vents, sunlights, etc to look for bubbles/leaks.  (Try to picture a air blown santa lawn ornament) You will be creating a positive pressure tank and any leaks should be found. 

There will be air loss underneath if your pipes, wires, hoses etc are not sealed, but the blower brings in more air than what should normally be expelled. 

If you have access to a floor dryer or carpet dryer you can do nearly the same thing yourself. A piece of plywood with a hole and duct the blower to a window. Duct the plywood to a window and turn on the blower. Should do the same thing. Probably less then $300 to do that and you don't have to tow it somewhere.  

I toured the manufacturing facility of the last trailer that I owned and they did a pressure test on every trailer before it left the factory. They had a fixture that fit the doorway and would blow smoke into the trailer and they would look for that. So I don't see why a spray bottle and air would work.