I never liked keeping catfish because they are so hard to clean and kill. I refuse to fillet a live fish. I am convinced that fish do feel pain.
That is, I did not like doing it until I learned this method of killing them instantly.
Basically, you make a small slit over the soft spot on their head between their eyes. Then slide a thin piece of wire into the soft spot, destroying the fishes brain and central nervous system.
The fish will shutter for a few seconds and then go limp. Large catfish require a long piece of wire.
Here is a video I made on how to do it: