I have found that the best place to do a join up exercise is in the pasture. I have had horses that would join up quickly in the round pen, but once they are turned out revert to their old hard to catch selves. But, if I do the join up in their pasture, the quickly learn that I can move them away anywhere, and learn to actually join up regardless of where we are. This does not require any whips or lead ropes or anything really. Just push the horse around the pasture with your body language, make them change directions as often as you can. Often the horse never leaves a walk, and I never do.
You can use the position of your body in relation to theirs to turn them. When they are going off to the left, let's say, you just position yourself in front of their drive line, and regardless of how far away they are, they will turn and go right. This method requires an understanding of how horse's communicate with each other through body language, but it can be used in the pasture without the stress of doing it in a round pen. You carry it out pretty much the same way as you would in a round pen, but the pen is much larger, and it will require more work on your part, but generally it works fairly quick. When the horse turns and faces you, stop for a second then take a couple of steps backwards. If the horse follows, with a couple of steps toward you, stop and remain there for a few seconds. If the horse does not pursue you, but just stands there give it a couple of seconds off then push it away by walking straight toward it. If it does not move off, great walk up to it rub its head for a moment then walk off. More often than not, the horse will follow you off. If the horse moves off, follow it turning it back and forth. Just keep repeating the exercise until the horse either walks up to you, or allows you to walk up to it. Rub its head and walk off.
The reason that I say just rub its head and leave is because I don't want the horse to learn that every time that it sees me, I am going to catch it and do something with it. I want them to learn that I may just want to rub its head tell it good boy or girl and leave. I may catch the horse, and groom it then turn it loose again, but that doesn't mean that I won't go catch him/her again 30 minutes later and actually work on something, I just don't want the horse to automatically think that if I catch them, we're going to work on something. I want them to look forward to being with me, no matter what I plan on doing.
The only downfall to this type of join up is it may be time consuming, depending on the horse. I've seen some horses do it in 10-15 minutes, and others take hours. But it does not stress them out because you are not pushing them hard, like you would be in a round pen. If you try this methods, be prepared to take however long it takes to complete it. Just go slow, and you won't tire yourself or the horse.