We love to get all up on our balls when having "gentleman's time," but would you slap yourself in the sack? That seems extreme. Well, someone's playing his own dominatrix.
Since HotRob0021's mistress wasn't there to paddle and thwap him while he masturbates, he took the role on himself, giving himself a hardy whallop at the start of the film. The rest of the movie is pretty standar issue as he jerks and works his ass over with a dildo before coming all over his bed. It's a fun time, but a soundtrack of someone berating him certainly would have added to the excitement. You shouldn't hit yourself when there's someone willing to do the job!
·Me Wishing Mistress Was There to Train Me (xtube.com)