I tried that once myself. I used a commercial gas powered blower, and a adapter made of plywood. I waited for a calm morning then I taped the plywood piece to an open window. Started the blower, stuck the nozzle into the hole and left it idle. For a soap solution, I used a 5 gallon bucket with dish soap, dawn I think, and water. I then used my camper-truck wash brush to "wash" the camper down. It worked! I had bubbles everywhere. I was freaking out! bubbles at every window, air conditioner, the door, the compartment openings, etc. Finally in disgust I shut it down and resigned myself to the thought I owned a strainer for a camper. After washing and rinsing off the camper, waxing it, and generally thinking I'm going to have to look for a new camper, I sat down with a favorite beverage. I think best with a cold beverage
. It dawned on me that in the videos I saw, those areas were taped off to prevent false leaks. Yep devil is in the details. The videos showed the window openings taped on the trim, the doors taped at the hinges and so on.
Bottom line I never did test again....I'm not allowed. In the process, the blower really jacked up my wifes curtains around the window, and blew the decorations off the table.