Trigger manipulation is different for everyone. One of the biggest issues I have seen was people squeezing with their entire hand. With a traditional stock rifle (not an AR or variant with pistol style grip) your firing hand should be barely more than resting on the stock. Not loose, but not “gripping” it. This will allow you to manipulate the trigger without having a tense hand. Its easier to concentrate on moving specific muscles when your entire hand isn’t tensed. The other issue is the trigger finger movement itself. Everyone wants to do the ‘hook’ on the trigger, and that isn’t necessarily the best. If you look at how your finger moves, the tip of your finger moves in an arc. You can’t force it to pull straight back. Knowing that makes a difference. This is why we teach a slow steady trigger squeeze, it allows you to compensate for the arc your finger moves in. Some people manipulate the trigger with the tip of their finger, some use the pad, others lay the joint over the trigger. I have seen people with large hands go all the way to the mid point of their 2nd “pad” and have excellent trigger control. Try moving your finger to different places on the trigger and see what works.
Breathing is a key component. Controling it isn’t natural. Learning your natural breathing cycle will assist in finding your ‘sweet spot’ of a natural respiratory pause. Some people don’t have a pause between breaths. These individuals need to learn where their slowest point is and capitalize on that. Yes, you can teach yourself to slow down breathing, but, the bodies natural response to slowed breathing or holding your breath is one of “panic”. The fine motor skills are first to go and fine motor skills is what we are concentrating on.
With your fingers being numb or reduced sensation, you will have a more difficult time mastering the feel of consistent trigger manipulation. Don’t let this dissuade or discourage you! Its still possible to “teach” your finger to do what you want it to. Consistency is key. When learning trigger manipulation, I prefer to fire 1 round and verify where it impacted. Binos or a spotting scope is easiest. Once you get a good shot, think about everything you did on that shot, how everything felt and then duplicate it. If your next round is off target, analyze what was different between the 2 shots.
As previously stated, dry firing just WORKS. Best way to teach a controlled trigger manipulation is to get into a good prone position, nice and solid, and balance a spend cartidge on the end of the barrel. Now squeeze the trigger. The cartidge should fall off when the firing pin strikes, not before. You’ll need some one to help you with this.
I taught many, many Marines to dry fire at a live target; the TV. This was more for handguns and rapid target acquisition for AR platform/shotguns. Once you have your draw from holster, stance and sight alignment down pat, you ensure you have an empty/cleared weapon, fire up the TV and watch the news. Everytime they pan from one newscaster to another you draw, acquire and dry fire. Its more difficult to do with a traditional rifle and doesn’t fit THIS application, but it is quite effective for fine tuning pistol shooting and shotgun skills.
Just my $0.02