Crush their heads. One half turn of the crank every 5 minutes until the crank can be turned no further.
I could never do that or watch it being done. I’m too civilized or Americanized, I guess. If I have to defend myself using lethal force, yes, I could do that, against a dog, against a man, but not this sort of torture. One must be capable of fully dehumanizing the recipient first.