I have been a firearms trainer of one stripe or another for 51 years. The process of training people to use firearms is far more complex than it appears on the surface. It involves mechanics, physics, psysiology, neural muscular learning, and conditioning. Then you must deal with law and ethics, dynamics of adult learning, mindset, the psychology of use of force, the effects of stress, and critical decision making under pressure. Perhaps the most important skill of the trainer is to understand what your students are seeing and experiencing when using the firearm. To add complexity, every student is different with different capacities for learning. Skills are built with a building block approach done in a logical sequence.
Instructors tend to have pretty big egos. That is not surprising given the nature of firearms training. But we must never forget, training is NOT about the instructor. It IS all about the student and making the student successful with desired outcomes. The cowboy instructor who is "all hat and no cows" can do more harm than good. The best instructors I ever had were extremely competent and experienced but soft spoken, like Carlos Hathcock, Steve Gilcrest, and Kyle Lamb to name a few. They were effective because student success was their focus.
I have met a good number of instructors over the years who managed to get through an instructor course but that's as far as their training went. To be a good insructor you must seek continuing education opportunities to stay current and to develop your effectiveness as an instructor.
Only a small prcentage of your students will take their training to the next level. Most will do the minimum or take one course, which is why we really need to hammer home safety and the fundamentals from the outset. It may be the only formal training they ever get.