So yeah, that would cause us to get called out multiple times if we only used the spray. Here's what we would have to do. Each of us had a de-webber that would extend like, 10' or so. We also had our normal pressure-canister of bug-killer (the stuff that is preventative and lasts 30 days or so). Using the dewebber, we'd knock the nest down, and then simply spray using our preventative on where the nest was. Wasps return home based on memory, so they'd eventually land in the preventative spray and die that way.
------- vietnam flashback follows ------------------
Biggest nest I've had to deal with was larger than a volleyball, and was on a mobile home. There was no "cover" for me, and there were an assload of wasps just flying around. Our dewebbers were bright yellow, and made a great target for wasps (better than us!). Every time I got close to this nest, however, wasps would not only go after my distraction-wand, but after me as well. So what to do if I can't get close to it?
I know that wasps need to have time to land before stinging. Also, we were required to wear long-sleeve shirts and pants. Our only exposed skin was hands and head. Most of us wore hats as well (Everything company-issued). I was a good distance away, so I just started running, with my wand joust-style up in the air aimed at the nest. The instant I hit it, a HUGE BURST of wasps exploded from the nest as it fell, and I swung my dewebber away from me as I turned and ran the fuck away from the huge mess I just caused. Of course, I was dragging the wand behind me in the grass, looking for wasps on my hands and trying to pay attention to anything in my hair or on my face. Once I was far enough away, I dropped the wand and checked my clothes for wasps. None of the bastards were on me, thank goodness. There were quite a few attacking the yellow tip on my dewebber, but those were easy to brush off into the grass. Looking back at the mobile home, there was a really large cloud of pissed off wasps I now had to deal with.
The majority of wasps are pissed off for not very long before they determine there's no threat nearby (cocky bastards), so I took this time to walk back to my truck, prepare my preventative spray, and then arm myself with one can in each hand of the insta-kill spray. I essentially respecced from melee to ranged.
The thing about the insta-kill spray, is that it knocks wasps out of the air immediately. They fall to the ground and sting whatever is in reach, before dying within two minutes after contact. This was a day I was grateful for wearing (steeltoed) thick workboots. Also, I taped the cuffs of my pants to my boots, to prevent any crawlers from getting up there (not likely with the spray, but why chance it).
So, I walked toward the cloud, guns blazing. My first spray knocked directly into the middle of the cloud knocked down a visible hole, so I just went all-out. I used up 6 cans of the stuff before most of the cloud was gone. The grass looked like it was moving; so many dying wasps exercising their stingers for the last time in their lives. The still active nest, lying on the ground was the final target, of course. Amazingly enough, it still held its round shape, except for a nice dewebber-sized dent in the side. Apparently paper doesn't hold too well to vinyl. I soaked that motherfucker until it was flat.
I finished off the massacre by spraying preventative spray all over the area where the nest was. Mind you, the whole time this was happening, wasps were returning from their scout-missions, wondering what happened to their castle-sized nest. Whenever a nest is knocked down, wasps will try to rebuild on the same spot, so eventually a nice gathering of wasps were getting covered in the spray. It's slow-acting, with the intent that the spray will "accidentally" be applied to other insect that touch each other. Good stuff, but damn it's slow.
The next month for my regular service call, I inspected the area. Not one wasp was in the area. Mission complete.
Also, still to this day, I have never been stung by a wasp or bee.