TXAZ, I've used the shop vac in our pantry to get a mouse infestation under control. My wife saw one running in there so I got the vac out and nozzled him right up...and 3 more of his buddies! The trip through the vac hose killed them all too.
As a pilot for more than 40 years, I was just short of being an "Ace"...also found the vac useful on cool days when the flies that get inside can't move so fast, and with no splatter on the kitchen window glass!
Lastly, I've tried corn meal, and #12 shot in .45 Colt brass and fired through my Ruger NV with minimal results other than nicking up the fascia on our cabin with the #12 shot. With either, I had to be within a foot or two to have any chance of knocking them down. I'll try that suggestion of ground walnut shells used in my brass tumbler some time.
Best regards, Rod