While my coach is awaiting deployment as an RV, it is pinch hitting as the local wasp magnet, safe house, and recreation facility.
Mind you, I wish them no harm, just want them to relocate.
Also they represent an absolute and total deterrent to any hope for help.
After 10+ cans of wasp spray, 3 busted fly swatters, and expensive traps, I decided I would attempt to be smarter than they are.
Brief research proved not very helpful other than find the nests and treat them.

The first major infestation was the A/C unit on the roof.
They knew it would be hard to get to, and it was.
But after removing the cover and spraying they seem to be avoiding (can you hear me knocking on wood?)

Next, and well hidden, was the front frame. After spraying several times nothing worked.
Until I started blocking holes with steel wool.
Rusted after some time, I ended up opting for foam spray.
Concerned about trapping moisture, I choose the lessor of two evils.
Thinking there were only a couple, ended up being a challenge to find them all.
You may see the nests near the hole, but you'll never see the huge nests farther in the frame, or be able to spray them without special equipment.
And then the ones on vacation return.

Next, after continually spraying the oven vents for years, I upped the ante and placed screens cut to fit under the outer cover.
Intention is to eventually screen all exposed louvers and favorite haunts, generator, exhaust vent (can't get screw out), propane tank area, and fridge cover.
Yes, concerned about air flow but that's only an issue if you use things, not parked for 10 years.
Also on the list is rubber seals on the shore power lid and other swing or removable panels. They don't need much room to invite themselves in.

Oh, one they were good at giving me a decoys.
In the genset area I had knocked down several nests hanging just inside near the top.
Tracing a couple years later turned out the biggest nest was behind the foam insulation surrounding the genset, near the front top where it had separated from the body.

The two requiring Sherlock Holmes skills were the odd shaped tubes running along the bottom side of the coach after the rubber covers were lost.
One of the last ones was the area where the body is supported by the frame. Still have a few of those to go.

As I uncover more of their fox holes I will update.

Probably not a problem if you actually use your coach, but for me priority #1 and prerequisite for working on it.
They even built one behind the inside dash as I had left the engine cover off.

Oh, one I'm not sure about. Seen the buggers crawling inside around the A/C lines in the front. Not sure I've got that one under control.
Hint, if you're having trouble locating the nest, just look for the mud or whatever they leave behind after they land going home.

May be due to my location near a creek. I'm sure much more prone to unused coaches.

I will consider myself with this singular expertise on GMC Motorhomes, and nothing else, until I hear another suggestion.
Will gladly relinquish the crown for any help whatsoever.

Please don't ask how many hours I have in this project, or give my significant other a hint how much time I was wasting.

Be still my heart.
You've knocked $50 off my annual wasp budget!
Ever since reading your tip I've had the Grass Roots "Where were you when I needed you"
In my head and can't get it out.

Now, save what's left of my sanity.
Tell me it works for chiggers.
The wasps don't bite.
The chiggers do, right where you don't want to be bite or scratch.
The bites are 10X worse than mosquito and take forever to go away, actually leaving scars!
The are my ultimate arch rival, and an even longer battle.

Will it work on those or do you know of another cure?
Forever grateful

Jim