I've done the same thing. I had a nest in an outside wall of my house. I tried bug spray several times and they never seemed bothered. Finally, I rigged up the shop vac, flipped in on for 10 minutes, and they were gone.
The other strategy that seems to work well is using a squirt gun loaded with a dish soap and water solution. The soap sufficates them and isn't too bad for the environment. I have a big old super soaker that I use /w3tcompact/icons/smile.gif.
I've been known to do the gas and match thing too /w3tcompact/icons/smile.gif.
-Chris