I have blitzed them (wasp killer)several times at very close distance outside and it kills them fast. But I don't want to plug the entrance hole because then many will be trapped in the garage walls and looking for an exit.
No matter how many I kill more and more keep coming. They smell the spray residue and go elsewhere. I have emptied two full cans of wasp killer. I'm not certain if you call these wasps or yellow jackets or something else. They are a bit smaller and so far seem docile. I am very close to them spraying and none have come after me for revenge (knock on wood).
They are not like the usual wasps I fight every year, that put up actual wasp nests - which I find much easier to destroy. I never had any hiding inside the building. They remind me more of ground wasps that go into a hole in the ground. Usual wasps will immediately pursue me and buzz angrily. These just seem upset that they can't get inside., and fly around aimlessly.
The garage itself is somewhat heated and rarely gets below freezing in winter - so I'm afraid they will survive the winter if I don't get rid of them now. ANY suggestions that won't kill me or destroy the garage. Help. this has been one crazy year- weather wise. Which I think is way diverse kinds of insects etc are making homes where they didn't before. I have lived here 47 years and never had wasps breach the walls (brick on all sides).