Reignmaker - you do a "remarkably"
good job of describing the process.
I have more to add.
I also do another step - it's done with the NH programs I flollow. You go beyond asking them to flex and havbe them turn away from you while following the "flex". To do this, you take the lead line on the opposite side from the handler. you step back aaway from the horse while asking for a flex away from you and use whatever cue you use to encouraage movement (I cluck). The horse flexes, follows his nose as he moves and turns away from the handler, coming alll the way around to face you.
Do from both sides.
Then take it a to next level. Ask for a flex and turn away from you but as horse faces the handler, the handler asks the horse to lounge from that position. Both sides. Depending on what level you are at whith the NH stuff and with whom, you are already doing this...
Then, again ask for a flex and turn, but as the horse starts to lounge the handler just steps back and "drives" for a couple of strides (w/ the one line on the inside), then steps back to the center to continue lounging. After driving a couple steps, handler moves back to center of lounging area and halts horse, praise in whatever manner you do and repeat. No problem if horse is confused - just ask for another flex (requires handler to move around the horse) and turn and "drive". Horse will "get" it - as you continue, believe me. Stop and redo. Both sides. If horse really upset, move back to hip and behind in more gradual steps. Just takes a little longer - but can be accomplished in the same workout.
Since this horse is already confused - maybe practice with a handler w/ two lines (sounds corny, can be hilarious but it does work!) without the horse. Because now you are ready for the horse to work with two lines. You will still do the same as ABOVE, just with two lines. Only when you step back behind to drive, you pick up contact with the line that was on the outside and keep horse going for a step or two in a straight line. Then release, stop, praise, etc. I think you understand?
IF horse is still "spinning" to face you, he may not be ready for this step yet. And you need to back up again.
OR you may want to "cowboy" him - litterally take hold of the lines and re-straighten him out. I DON"T consider this step "cowboying" - but have had some friends say it is. I find about 1/2 of the ponies I start need this step - strongly. They are usually the more reactive ponies and have reacted strongly or spookily to every step of training! They take longer to get to this step, but once they "get it", they usually retain it. When you do this, do it next to the fence, so when you have him swing to the inside to face you, you pull his head back towards the fence and encourage a step or two. It takes practice to figure out how to handle the two lines when you first start and going from slack to tight to slack is part of what causes them to want to "spin" and face you. That's why practicing with a helper (who should follow the "feel" or taking up the slack every time you do so that you see what I mean, that's what's so funny), helps so much, LOL. Again, it takes longer, with more steps for these ponies to allow me to get behind them and stay there for any length of time. I just keep working on it... Usually going back and forth from lounging w/ two lines, to crossing behind them as we switch directions, to lounging with two lines. OR at this stage, you helper if you have one, can hold the horse straight (walk beside) as you start driving. But I don't usually have a helper and I go from the lounging to the driving steps interchangably (back and forth) - so it's more difficult to "use" a helper. That's when "keeping" them on the fence, is what helps. Another step - as you switch from lounging, to moving behind the hip to drive and they try to face you, turn them into the fence and keep them going the new directions for a step of two. You can even go back and forth - where if when you turn into the fence and he wants to continue around and face you - turn him back into the fence and then halt. You stay behind him, and to praise him, step forward and praise him by petting him on the hip rather than going up to his head/face. THEN, step into your lounging position, ask him to start, step towards him to drive him using outside line to keep him on the fence a couple of steps, turn him into the fence and straighten back out and halt again.
Each of these steps is getting him used to you beng behind him.
The next step i use is the one that reignmaker does with the obstacles to give you something to drive around.
Practicing this in an enclosed space is MUCH MUCH easier. At any time, if horse gets too confused or you really get tangled up, DROP the lines (especially the one that's on the outside from where your were working), take a deep breath, praise your horse when you catch him again, and start over... The horse doesn't get away, dropping the line (s) at this stage isn't going to be a problem (if I drop the outside one when the horse is upset, I find it doesn't usually get stepped on).
O - at this stage, I don't have the lines run thru the rings on a surcingle and often I don't even have a surcingle on them yet... That's later - after I have them "driving"... Some folks have told me that it's easier for them if the lines are thru the surcingle, but I find that that makes me want to hang onto the lines more strongly and it's harder to "lounge" them and go back and forth between lounging and "driving"... Later, I will pick a side (bad, bad me - I generally always choose the left) and leave that line out of the surcingle rings when I start with the surcingle. That way, if there is a problem with "driving" - I can turn the "outside"(right) line loose (let it go) and just lounge... When horse calms down (or I do or whatever), I start again. When I'm ready to drive to the right, I take the right line out of the surcingle ring and start with lounging w/ the "outside" (now the left line) in the surcingle ring. You can still turn and switch between lounging and "driving" - but if there is a problem, horse spins to face you or spooks, you turn the line loose that's in the surcingle ring and you are back to what you are both familiar with - lounging...
A good book or video - there are really several - but honestly none that I've found really address the problem you are having. That is a problem I had when I first started too, again, especially w/ my more reactive ponies/horses. And none covers ground driving steps the way Reignmaker and I have both described... It's like most books think every horse is "ez" and gets it automatically, LOL.