Put the chain through the left lower ring on the halter, then bring it over the bridge of the nose, and attach the clasp to the lower ring on the right side of the halter. If the animal acts up, a quick jerk on the lead rope will sometimes change its ill ways. This chain can also be placed under the upper lip, over the gums. Give a quick snap only when he acts up. Scotch hobbles and side lines can be used to tie up legs or to hobble the legs together, but should be employed only by people with the skills to use them.
Some farriers use stocks to restrain the animal for trimming and shoeing.
The best way to train a mule or horse not to kick is desensitizing the animal to the fear stimulus by getting him so used to it that he no longer takes notice. In the long run, the skills of a good trainer can be of great help. I can't stress strongly enough the idea that you should not try to break a kicker by yourself. Not to disappoint you, but some horses and mules are just plain nuts. They have a total inability to control their rational processes.