There are a lot of people who use ground driving and long line work for starting their young horses. It is a good way to get them moving properly and comfortably with tack on, teaching them to balance themselves with the saddle on their back, what the reins and the bit are for and what cues and body language mean to them when we ask for different things. It also gives us a visual idea of how the horse is actually moving, since we don't get to watch ourselves ride and it is sometimes rare to get pictures, let alone quality video.
Lately in Bloggerland there are a lot of us finding ourselves, out of the saddle and back on the ground trying to fix things that seem to be coming unraveled... *Raises hand, Been there, done that.* It seems when I get ON the horse, there is so much for me to think about, so much I am trying to do, things I am trying to remember, focus on, DO, Don't do, work on, let slide and it can get overwhelming. There's too much going on between the ears up there and Unless there is a drastic change in how things FEEL? Forget it. Driving, ground driving and long line work? Take away the legs, the weight, the seat and you take away a lot of the things we as riders may think about when we are on our horse.
So where to start?
First off you need some decent lines to work with. A bridle which you probably already have and either a surcingle or a saddle will do. You'll want to use a snaffle bit as it works on the corners of the horses mouth, is not a leverage bit and therefore more mild. You want something your horse can accept calmly, rather than too much bit, which will show in their reluctance to move forward. You can also use a lunging type whip too if you need something to help motivate your horse to move forward.
My lines are made of the polyester braided rope found at most hardware stores. The 100 foot length will give you 2 lines 35 feet long for working the horse and another 30 foot line for lunging. Snaps and all, you're looking at around $15-$20 out the door. Heavier rope can be used and will give a little different feel to both you and your horse, but keep in mind that the snaps and the knot holding them on, may not go through the rings on the surcingle if you use one.
Surcingles are also another fairly cheap tool to acquire. I bought mine online from one of the many companies I get catalogs from- Jeffers Equine, Valley Vet, SmartPak, Stateline, Big Dee's, Dover Schneiders... Shopping around you can find them on sale for anywhere around $15-$25 for the basic model, synthetic, lots of big rings, comes with the girth, blah, blah, blah. This will fit a large variety of horses in different sizes. Mine fits a standard Arabian or QH, up to (barely) fitting my WB mare.
The thing I like about surcingles and why I prefer them to saddles for ground driving /long line (GD/LL) work, is because you have options as to where to put your reins thru them. Saddles you are either stuck with just the stirrups or the rings on a breastcollar. Running the lines thru the rings on the breastcollar works, but it can be uncomfortable to the horse. Any time you have to pull or tug on the lines, it's either going with the hair as you pull or against the hair as you release. Sooner or later the horse is going to become a bit irritated because it will be sore.
Running the lines thru the stirrups on either an English or western saddle, you need to secure them underneath to limit the 'swing' and keep the stirrups closer to the horses side. Baling twine works well for this, but putting it on a green horse or a re-hab horse, can be a little hairy if they aren't used to or don't like things going under their belly. Depending on how long or short your legs are- the stirrups will put the lines going down and whenever you take up contact, the pressure will be coming from down, not up where your hands will be when you are riding. Saddles will still work, but I prefer a surcingle if available or even a driving harness saddle. The harness saddle will allow you to run the lines thru the tugs for more lateral work or the turrets for regular work.
I have also seen the terms Ground Diving and Long Lining thrown around almost as if they are interchangeable. There are differences in the two and you can go from ground driving to long lining and back again. Ground driving is basically driving the horse forward, from the ground. You are behind them much as if you were sitting on a cart and you follow them around the arena or round pen, wherever you are working. Long line work is different as they are further out towards the ends of the lines. You can ask for a jog, trot, lope or canter and still control things as they go around you on a circle much like lunging.
For a young horse just starting out or even an older horse going thru re-hab, I like to start out in a round pen. If they are to freak out and lose their mind- they have a place to run and you can quietly wait them out. They aren't really going anywhere even if they happen to pull the lines thru your hands and take off. If they spin around to face you and end up wound up in the lines? Again, there's not a lot of options for them if their 'flight mode' kicks in.