When I was teaching full time I had an Instructor's class every Monday night. We would do a hard warm up of the basics, followed by going over the curriculum from a belt, each week we did a different level, this way I ensured that we were always working on getting the material down better for the students. They all had a binder that they brough to the class, and the last half hour was spent with me giving them a handout on something, whether it be a drill, the written breakdown on a form or set, an interesting article. In that last half hour we would also go into how to teach, I showed them how to plan a lesson, and organize their thoughts in a well laid out manner. We also had a 2 twice a yr instructor's boot camp, where I showed them different material, went through all the belt levels, we worked on first aid as a refresher.
When I was looking at people to begin to learn how to be instructors I had a multi-tier system for them. They started off helping the beginner classes, and they were given the title Jr. Leader, they had to attend instructors class each week, and when they were on the floor with the beginner I had them wear a gray belt so that there would be no squabbles form people saying I don't want to learn for a person that is only a X belt. After 6 months if they were doing a good job they were admitted to the LIT's Leaders In Training. LIT's wore red belts and really helped with the beginners and intermediates. They were they people I would have go work with a belt group when I broke up the class to do their techniques. This allowed me to float aroound the room and correct little things as i saw them and go from one group to the next to teach the various material. If a person graduated for the LIT program they became Assiatant Instructor at the Black belt grading.