I prefer the Rogers technique as my main light technique and I am a right handed shooter. If I attempt to use the technique on a corner that opens to my right, if I activate the light I am going to blast myself with the light instead of lighting the unknown space I am trying to clear.
My choices here are to expose more of myself than necessary to get my light out past the corner, or to transition to the Harries technique which allows me to keep most of myself hidden while still allowing me to search the unknown space because the light is now to the right of my weapon. (For a wrong-handed shooter it would be the opposite.)
The world is a very big place and is full of all sorts of problems and issues. When you are trying to clear the average structure it will be almost impossible to use just one light technique to get the job done.
Having multiple techniques in your toolbox is vital for the defense minded individual. You will also encounter situations where none of the stated techniques is appropriate and you'll have to improvise one on the spot.
An example is if you have to look under something like a porch or a car. The FBI technique isn't going to be terribly useful here, but putting the light at waist level may work for you, or even putting it at knee level.
The most critical thing I can tell you at this point is that YOU MUST TRAIN DILLIGENTLY WITH EACH OF THESE TECHNIQUES TO HAVE ANY HOPE OF USING THEM UNDER STRESS. You cannot practice it once and get it down pat. Using a light in conjunction with a handgun is difficult and it will not come easy.
You need to spend considerable amounts of time practicing these techniques with an empty weapon inside a structure and also with live fire on the range. Thankfully you can practice the techniques with live fire during daylight if your range won't allow night shooting.
You need to practice engaging multiple targets with these techniques and you need to practice shooting on the move with these techniques.
You need to spend time searching a structure (like your house when nobody is home) in the dark and learning how the various angles and corners in your house make one technique a better option than the other. You need to practice getting into these techniques when drawing from concealment….
Starting to see my point? You need to train on these techniques in a wide variety of situations and scenarios that you can find yourself in.
It is also necessary to practice weapon manipulations with the light. Most of the techniques leave you shooting the weapon with one hand, but when the time comes to reload or clear a malfunction you are going to want to use both hands. This means you have to do something with that light.
A lot of people teach tucking the light under the strong arm and then using the weak hand as normal and this is very effective. Some teach putting the light back into its holster (assuming you are carrying your hand held light in a dedicated readily accessible light holster)
Some teach putting the light in your mouth. Some teach dropping the light on the ground and then simply drawing a second light from your belt. Generally the folks I've met who use this tactic carry a minimum of THREE lights on them at all times. My personal favorite technique is to use the lanyard or a large key-ring on the weapon light.
If you remember I listed the lanyard available from the factory on the 6Z/Z2 combat lights as a desirable feature. It is a desirable feature because it allows you to let go of the light and use your weak hand to do something like reload your weapon or clear a malfunction without losing the light and it allows you to get the light back into play very quickly when you are loaded up again.
Now some people's physiology is not suited to performing something like a reload with a light strapped to the inside of their palm like I do. Because of this you really need to be able to do the tuck or the reholster even if your main lights have a lanyard on them.
Again, knowing these techniques in concept is not difficult… but reading a description of them or even seeing them used is not going to prepare you to use them under stress.
IF you do not make a discipline of training on this stuff you will NOT be able to use it effectively. Worse still, you may fall victim to a common foul up.
One of the most problematic aspects of using a hand-held light with a handgun is indexing the light and the sights of the weapon on the same spot. Often individuals only manage to get the weapon indexed properly initially.
Under stress they have a bad habit of noticing that their light is indexed improperly and then moving the light until the hotspot is where they want it… but they also move the weapon.
Under stress they aren't looking at their sights and are instead treating the light like a really big laser sight and are assuming that the light and the weapon are pointed at the same place. They then proceed to launch rounds into the dirt, into the walls, over the head of the target, over the berm, and anywhere else you can imagine except the intended target.
In a real fight you won't have an instructor by your side spotting your shots and telling you what you are doing wrong.
Again: It is CRITICAL that you train on these techniques. There are no shortcuts or magic fixes.
Weapon lights, of course, make all of this much simpler. You don't have to worry about all these complex hand techniques and you can use a normal two handed hold with a weapon light… and you can also perform standard weapon manipulation drills without worrying about what you do with the light.
BUT… that doesn't mean you don't need handheld light or handheld light techniques if you have a weapon light. Weapon lights are useful in only in certain narrow circumstances.
If you have to have your weapon out and pointed at somebody a weapon light is a good thing… but that's not an appropriate action for the majority of circumstances.
Naturally you can't go around pointing firearms at suspicious situations so depending on a weapon light as your ONLY light is a really bad idea.
While on the topic of weapon lights for handguns it's critical to mention something else: If you are going to use a weapon mounted light on your handgun, use a holster that can accommodate your weapon mounted light. This business of putting the light on after you clear leather and taking it back off when you need to holster up is ASKING for problems.
A number of police officers have managed to shoot themselves in the hand while attempting to take weapon lights on and off under stress. If you don't have a holster that can accommodate a weapon mounted light, you can still use the weapon mounted light with the FBI or neck index techniques very well.