Are you sure those are wasp's or hornets? Looks like an Africanized honey bee swarm, in which case, buried under all those bugs is the queen, and they are looking for a new home.
For yellow jackets aka Hornets I do like the vacuum cleaner.
But the first thing is to dress for success.
Put on a pair of hard boots (not tennis shoes) Pull pants legs down over boots, ductape the seam so they can't crawl up your legs. Heavy shirt tucked into your jeans. Gloves, duct tape them onto the shirtsleeves, again for leak protection.
Finish up with hat, a hand towel around your throat, and mosquito headnet.
This year I had one get inside the netting that slipped through the Y of my shirt.
So wrap a towel around neck, and make sure headnet is pulled well down over it. No gaps = no stings quick, hasty or careless = pain.
I suspect in that location that Carb Cleaner, spray brake cleaner, or such would work just fine to knock them down. BTW consider a 10' extention for the vacumn, 1 1/2" pvc would be my first choice.
Once you have them IN the vacumn, spray some flying insect killer down the pipe with it still running. Then let the vacumn partially suck a plastic grocery bag down the pipe. Idea is you do NOT want them coming back out again. Turn it off, let it sit for a few hours, and LISTEN!
If they are dead, it will be quiet, if they are alive, they HUM.