PD is training more sluts to be expert cock-suckers. There is an entire skill set that they need to perform up to his standards. A good slut needs to be able to dance, suffer and suck. Cumming on command is another must. Charlotte Vale already has the basics down. She is a candidate for his advanced classes. When she shakes her ass the beat is provided by the electrodes running into her. When she sucks she does it like a professional with a lot of practice. He knows that her holes are ready for anything and he also knows how to push those limits.
Charlotte is perfect for the kind of bondage PD likes. Both physically and mentally she is suited to submission. When he hurts her the pain makes endorphins flood her body. Her mind starts racing at first, with anticipation for more, then relaxes into the calming realization that she is powerless. The power that he commands her with makes her pussy wet. It is her fantasy to serve a strong man and PD makes that a reality.