Outdoor Pest Control - Wasps & hornets in trailers

I have 2 utility trailers (both aluminum, if it matters) and wasps & hornets just love to use the many holes & open ends to establish nests inside the frame & rail tubing. Also in & around the hitch & jack tube.
I've considered spraying Sevin into every hole & tube I can access and have also considered pumping cans of expanding foam into the tube openings to seal them.

In the spring I regularly patrol the house & outbuilding & spray carburetor cleaner (instant kill) on any new nests but it looks like I missed their activities in my trailers.

Anybody with other or better solutions to these nuisances?

The expanding foam will work, as will making "pegs" of wood and driving them in the holes and frame members to keep them out. Keep the ball hitch well greased. You need it greased and the wasps can't build on the grease. Keep the landing gear well greased and sprayed with either oil or WD40.
I'm having to do the same thing on my wife's clothes line post cross tees. Tap on it and wasps pour out of it. I'll probably go with the expanding foam once I "terminate" their lease.

After the fom sets up you need to remove some of it and apply bondo. The foam will deterioriate with exposure to the sun and rain. The bondo will stick to the metal and seal the foam. Or you could forgo the foam and just stuff plastic bags in the holes then the bondo. The bags keep you from having to use too much bondo. I would make the bondo at least 1/2 inch thick.

No exposure worries on these tubes. They either face down (rail posts) or are sealed at the ends (frame).
The thing I like about the foam is when I need to put a hook in a hole the foam won't offer much resistance, but it still seals the rest of the tubing from nesting pests.