We had a European Wasp nest in our front yard a few years ago in/under a pile of lawn clippings. Having 2 young kids at the time I was pretty keen to see it gone, tried the dust thing and it didn't really seem to worry them so called a bloke I found in the phone book. This bloke turned up mid afternoon, wearing shorts, singlet and thongs, which was ok I thought, it was kinda warm and if you are wearing enough PPE it probably gets pretty warm. Anyway he had me point out where the nest was, he watched it for a bout 2 mins and went back to his car. He came back with a garden sprayer - just the cheap ones that you get from Bunnings for under $10, but the wand part was just the metal tube without the nozzle. Still in his shorts, singlet and thongs, I kid you not, he proceeded to wander over to the nest, plunge the wand into the middle of where the nest was, and lock the trigger open and walk away, lent against his car and lit a ciggy. To say the the wasps were unimpressed is probably an understatement, they came out and were having a good crack at the sprayer. After he finished his ciggy and we had had a chat about how many nests he was knocking over (about 4-5 per day apparently) and how he had NEVER been stung he said "they will all be dead in an hour, that will be $35, and do you happen to have a broom so I can get my sprayer back, or I can come back and get it tomorrow" I had a 2m boat hook that I fished out, again casual as you like he wandered over, hooked out the sprayer, packed it in his car and was gone.
I am not advocating that sort of approach, but I will never forget how mad I thought this guy was. I would suggest though, if you do want to get anything IN a nest, the pressure sprayer did the job. I reckon it was probably only about 1/3 full so there was plenty of room to build up enough pressure to empty it. Would probably work with petrol if you wanted to try that, but I would say the sprayer would only be good for one use, it would probably eat vital parts of the sprayer.
Cheers
Rod