If they hacking or cutting a mans cock or destroying it by any method it should be done when he is alive and in full charge of his senses. Doing it after death or when he's unconscious totally defeats the object.
He needs to see what is going to happen. He needs to feel the fear. Be made to believe he may have a way out. Experience all the emotions of fear. Then a brief sense of relief after a little cock pain. Then the terror when he is told his cock will be taken.
Then it should be slowly separated from his body making it as painful as possible