Reader explains how NXIVM trainers use covert hypnosis techniques 

They believe in neutro-linguistic programming (NLP), which in this case would be Ericksonian covert-hypnosis.  The first steps are for the controller to converse with you, preferably seated side by side, and subtly match your body language, which apparently goes a long way toward making most people trust the controller.  Then it escalates to things like shoulder taps, often in the context of a joke.  Eventually you feel like you have known the controller forever and are very much at ease with him.  Keith is supposed to be a master of this stuff.