I never heard of a "mud dauber" until we got into RVing. What do they look like, and what parts of the US & Canada do they hang out in? Around here, the closest thing is probably Yellow Jacket wasps. We have a couple of other kinds of wasps here, but the Yellow Jackets are really prevalent in the summer. I don't think they get into RVs though??
Come to think of it, once in a rare while, I have seen what they seem to call here, a mud wasp's nest. Haven't seen one right on or in any kind of a vent though.
My dad always used to say "never poke at a wasps nest." Decades later, I still haven't learned that. Owwww.....
Spray from 20' away seems to work better.