Within the world of tactics, training, and even gear, there tends to be three demographics: military, law enforcement, and civilian. Civilian, in this context, refers to armed citizens. Even law enforcement officers and military members are, of course, civilian when out of uniform or off duty. Most civilians who go armed are, of course, not among these uniformed professions. One of the issues that we deal with is an often inappropriate overlap between these three sectors in terms of training doctrine. It may be obvious, but a great deal of military and law enforcement training is not applicable to the civilian self-defense context (especially military).
I have no background in military and law enforcement and that leads me to have a direct lane in civilian self-defense. I am not experienced in nor interested in military or LEO doctrine. Now, granted, shooting is shooting, and good shooting is a similar skill set between all three sectors. However, the shooting is only one part of the whole puzzle that is self-defense and personal protection. Beyond this given skill set the vast majority of the doctrine is different.
There are more similarities between law enforcement and civilian context than between either of these and the military. Many of the well-known trainers in the field of firearms instruction are ex-military and that is not a problem as long as they are tailoring their teaching to the civilian context if they are teaching tactics to civilians. Again, the shooting tends to be fairly standard affair: if you take a carbine course with an ex-special forces guy the actual shooting skills should transfer over to your use of the carbine in a home defense role. Many of the better known trainers are indeed active duty or ex law enforcement or military.
My advice to people new to this endeavor is to seek out trainers who are relevant to the skill set you need. This does not mean that the ex-military guy is not a good choice, just verify that he is credible and that he is indeed tailoring his training to the civilian context. There are a lot of good instructors out there and, of course, a lot of horrible ones. My final word of advice here, though, is to get your priorities straight before beginning a search for training outlets. If you are a civilian concealed carrier, set that as your priority in attending training and in your own practice routine. While clearing structures with carbines or using night vision in a “night fighter” course may be quite entertaining, be sure that you are solid with the skill set that is actually going to be used in your real life if you need it: in particular your handgun.