Another thing that helps while lounging is literally changing directions - a lot. If you follow any of Clinton Anderson's teachings -it is one of the tips he passes along. Every couple of strides - switch directions. It is tiring! Then when tired, you can work with posing your horse as he gets "his air back".
Changing directions every few strides can also be hard on a young horse, so you do want to watch out for them. You don't want to injure their legs, but you can certainly do the direction changing in moderation.
Also, you can do direction changes while leading your horse. If he/she gets to jumping around (something that seems to be expected and/or allowed with minis/shetlands/arabians), you can change directions and expect them to be right at your side/shoulder. So he starts jumping excitedly, you turn 90* to the left and stride off. If he doesn't join you, he'll get a pretty sharp reminder - just from your halter and lead line. If you are working with a whip, reach behind you and tap him on either butt or lower legs - encouraging him to stay right up there with you. You can even change directions by doing a complete 180*.
As your horse learns where he is supposed to be, when he gets excited/jumping around - turn into him - moving him away from you in a turn. I have bumped them on the head between the eye/nostril and on the neck between the ear and the withers to encourage the turning away. Soon, they would rather do a "simple" straight line than be constantly jumping around. You could even associate your turn away/turn into with a "growl" or some other easy to remember noise that you make and utilize that at a show as a reminder and start to follow thru w/o then finishing your turn. Hopefully that helps to keep those feet on the ground.
This worked for us with the Shetland Xs that were shown in open shows at halter similar to a Sport Horse or Warm Blood breed (no acting up really allowed and very frowned upon). Foals/weanlings/yearlings were given some leeway, but not a lot - still affected final score which then affected placement in the ribbons.
Since I didn't train our Shetlands that went to the breed shows, I can't tell you how each was trained. But I know that the one stallion with a trainer in TX was allowed to be an idiot and I was most unhappy with that (at the Spooktacular show in TX in Oct 2012 and at Shetland Congress in July 2013). When he came home and still acted that way, we got into several "knock down, drag out" fights - in which he ended up upside down on the ground in a hurry. He soon learned to keep his front hooves on the ground - regardless of who was going by or what was going on. He also spent a lot of time with a "5th leg" (dropped & erect) and several times he had that "leg" tapped quite forcibly with a dressage whip. Not hard enough to injure him (he was a stallion and I did plan on some foals), but sure got his attention!!!! Again, didn't take long and he wasn't running circles around me with "5 legs"... He even learned VERY WELL to keep his mouth shut! He learned that all in less than a month as a breeding 2 yr old stallion - after his short show career. Wish he'd been taught that BEFORE his short show career - he may have done better, who knows?