How to fuck a girl so that your balls slap against her anus?

A Russian slut meets her friend's brother, and he invites her over to his place to fuck. She has a fantasy—she wants the guy to slap her asshole with his balls during sex. Hearing this, the guy is confused and goes to Google how to do it. At that moment, the hero's father appears and shows the girl how to slap and in what positions. Soon, his daughter joins them, and they have a hot FFM threesome, while our hero just jerks off to porn in another room.