It involves holding a tail, their head, and a hard surface.
Some may call it cruel... I'd rather not see another hole in any of my snakes... THAT'S cruel. Been there, done that. Like I said, the rat/mouse will be dead either way... I'm just helping along the process. You just need to have the stomach for it.
My snakes won't eat F/T consistently, so this is the way I go.
BTW, my method... zero chance of a snake injury.