Trapped k-9's for a lot of years without using a pistol, as I wanted a clean reset with no blood. Like KH, I used my yo-hoe. If you are trapping, chances are you have one. I didn't use it as the dispatch tool, but would rap them just above the base of the snout and this would stun them. Don't swing for the fences as it just takes a sharp rap is all. Then I placed my foot over the heart/lung area and stomped. Simple, quick and no holes or blood.
For the first few years, I shot all trapped animals. I had a very good catch rate for first sets, but my reset catch rate was not very good on k-9's. Talked with the fur buyer some (also a trapper) and told me to quit shooting the k-9's as the blood makes for a dirty set. After I quit shooting them, my reset catch rate went up. Just something to think about.