Coat your cock in something like extra strong minty toothpaste, leave it for 10 minutes then plunge your cock all the way into a jar of iced water. Put loads of ice in the water and loads of salt, the salt will make the water stay liquid at colder temperatures hence it's colder. Make it so cold that the ice doesnt melt anymore. Then after the 10 minutues plunge in. Hold your cock in there until the pain completely stops.
have fun