Grasp your penis firmly with one hand. Squeeze as hard as you can until the head of your penis pokes through the top and is ripe in color to the point your finger leaves an impression when poked. While still squeezing take your other hand (open palmed) and begin vigorously slapping the head of your penis in short quick but firm slaps. The slapping noise should resemble the sound you make when slapping a ketchup bottle. The point of this is to numb your penis to the point it feels like you are jerking off another mans penis.
Eric: "Yo bro."
Eric: "Have you tried to ketchup bottle yourself yet?"
Fred: "Dude I ketchup bottled my dick so hard last night, it felt like I was jerking off Channing Tatum!"
Eric: "My Nigga! Love that bro!"