Technically, most Minis have Shetland in their pedigree, it just depends on how "close" it is. I think my show gelding has it quite close, and he is the most forward, ambitious Mini I have!
(Personally, I also think that is what gives him the structure and movement he has, too.)
All of our horses first learn walk, trot, stop, set up, and stand cues with just the halter and the leadrope, the same as if you were doing Showmanship. Make sure you use the same verbal cues for EVERYTHING you do with the horse, lead into the stall, stand for trimming, trotting for the fun of it, etc. For us, one cluck is "walk", two quick clucks is "trot", and then also "ho" and "stand" (we use kiss for canter, as that is what our big horses are trained to do. That helps for CDE work eventually). To get them to trot in hand, use a whip long enough to reach behind you in your left hand while you lead with your right. As you "trot", if they don't follow, flick them in the flank with the whip while you give the verbal cue. All our horses know all of this before we even progress to the longe line. Then, when we make the transition, they know that when I cluck once, they should walk regardless of where I am in relation to them.
On the longe line, they learn the three speeds of trot by varying the size of the circle. The bigger the circle, the faster the trot (after they know "whoa" well). We start with the working trot, and I just want them to have a nice easy, forward trot. It doesn't matter really what the speed is for a while until they learn to maintain an even, balanced pace. When they have that down, I "reel" them in for the slow trot, all the while giving the verbal cue "jog" in a soothing voice. For the strong trot, I tell them "trot up" in a more animated voice. Eventually, I don't have to change the size of the circle, because they know the verbal cue and will respond to it readily. Even if you aren't going to show, teaching multiple speeds of trot is very helpful in general driving, and makes it more enjoyable when you can vary the speed.
I have had more lazy horses on the longe that I have had to get after with the whip, but if you are aiming it at their hock or hip, they will almost automatically move forward, just like their buddy in the paddock that gets after them to move. I usually don't have to "beat" my horses with the shaft of the whip, but just flick the lash at them, all the while using the verbal cue. Remember, you would rather be
told to clean your room than to have your mom drag you by the ear to do it, so always tell the horse
first. However, if he doesn't respond in a matter of seconds, reinforce with the whip. Eventually, he will decide that responding to the voice is "easier" that getting encouraged behind. Once he knows how to move forward on the longe line with the verbal cue and the whip reinforcement, then the progression to line driving will be much easier.
In some cases, I even line drive the first few times with the halter. This makes an easier transition for them as well. The more you can break up your training into smaller steps, the easier the horse can relate what he already knows to what he is learning that is different. You didn't learn your numbers and then jump directly into dividing them. You had to learn to add, subtract, and multiply them before you could divide them!
Myrna