The first thing you have to do is have diligence in not letting the squirrel jump off of you. Every time he jumps off of you you have to make sure to pick him up and put him back on you, in your pocket or inside your shirt and let him settle down. If you continue to do this he will learn to never leave you or your friends.
Once you have your squirrel trained to stay on you, you can begin the fun part of teaching him to fly from person to person. Start off with short distances, put him up on a door or somewhere a little high and encourage him to jump to you, do this repeatedly until he has it mastered and then gradually lengthen the the distance that his is jumping and the height as well. When you notice the squirrel about to jump, DON'T MOVE! If you do, and he misses, he may hesitate to jump to you the next time. Now he is ready to jump from person-to-person.