Off with Charlotte - SIRIUS Puppy Training Classic

As you can maybe tell, this video is a couple decades old.  We have since learned that this exercise is just as effective without bopping the dog on the nose, or even shouting.  If you say "Off" and your pup continues to mouth or paw at your hand just ignore them until they pull away.  As soon as they pull away you can reward them with the treat.  Gradually increase the duration of the Off, and they will quickly learn without the need to aversive corrections.