Get a girl naked..preferably one you dislike. Have her lie naked on the bed face down. Tell her you have to use the bathroom. While in the bathroom, shit just far enough out of your ass so the shit hangs a good couple inches. When you come out of the bathroom run and slide across her back like you would across the hood of a car.
I saw this Bitch i hated. So I decided to TURDle wax her!