Well, as far as I know from what I've experienced personally, and what I've read in books about join up you don't "teach" your horse to join up, its something they do naturally.
Join up is when the horse not only accept you as a fellow herd member, seeing you as a non-predator, but respects you and follows your lead willingly. What should happen is once he gives in, he will usually turn an ear to you or show a want to come near you, and at that point you should stop driving him away and adopt a passive or non-threatening stance. He should approach you completely with a lowered head. You should not have to step in his direction or lean in order to touch him, he should be right smack-dab by you. Once that has been established, he should follow you, no matter which direction you go or however fast your going. That shows you have truly joined up.
If he hesitates or doesn't come completely in, your supposed to send him out again until he makes up his mind as to whether he wants to be with you, or by himself.
I'd suggest doing join up without a line attached, such as in a round pen or rope off an arena into a round pen. If your horse has minimal to no training as far as ground work goes, I'd be sure that all the gates are securely shut in the arena you are using if you don't have a round pen in case he breaks out of your make-shift pen because he doesn't understand cues or for whatever reason.
As for truly understanding and accomplishing a successful join-up I'd suggest visiting www.parelli.com
and possibly look into ordered books and movies.
As for lunging, I'd suggest that minimally. Lunging gets boring and can put a lot of stress on the joints if over lunged. I'd suggest a maximum of about ten minutes of lunging a day from a personal point of view, while many other people I know would say 15 minutes and others would say a half hour. It all depends. I'd rather turn him loose in an arena after we join up to work him further instead of keeping a line on him all the time.