Hal's hypnosis only works on people he hadn't met before he was hypnotised.
This is why his boss looks the same, as do his friends.- This isn't Mass Guessing. Tony Robbins clearly states this while they're in the elevator together that from that point forward Hal will see the inner beauty of every new person he meets.
Hal and Tony never left the elevator.
Part of Tony Robbins' actual tools of trade is guided visual imagery, helping people emotionally associate themselves to the traits they desire. From the elevator scene onward, Hal is merely imagining everything that happens. Another tenet of Robbins' teaching is to anticipate and handle setbacks, meaning Hal will also have to imagine what if the hypnosis wore off (also known as an ecology check/future pacing).