Pretty sure he meant to use the gunpowder in the way it was intended, to eliminate your squirrel problem with extreme prejudice.
22 shorts will work with a minimum of noise. A good pellet rifle will also do the job even quieter.

But you can try this first if you don't like the other way.
Game warden told us to use a mixture of mayonnaise and cayenne pepper to get rid of a ground hog under a porch. Apparently they love the mayo and when the cayenne kicks in they run away and never come back. Worked for us in one day. I bet it probably works just as well on squirrels.