I would highly recommend that if you get the chance you attend a cowboy mounted shooting match and observe the mechanics involved.
Overview: basically you have a male or female on horseback with a single
45LC. They ride around a random course shooting balloons set in cones at various heights. This is a timed event so going like he**. They shoot 45 blanks which is nothing more than a crimped shell case loaded only
with black powder, no wad. You are steering this horse through a sharp turning course and shooting 10 balloons with 10 rounds
observation: So you have this 1200 pound horse bouncing you around at a trot, canter or gallop. you have to draw shoot 5, re holster, draw your other gun and shoot 5, and cross the timer. There are 50 different patterns that the range master chooses from. The range in order to break a balloon is only about 10 feet if you are exactly centered on the balloon. Oh and you are shooting one handed
Point of post: It really doesn't matter where your horses 4 feet are, or how you have your thumb wrapped( cause you don't shooting one handed). What matters is where the the barrel is pointed when it goes boom. This includes having to lead. While the target is not moving you and your horse are.
Yes if you have a chance, feet, breathing, two hands etc. etc. etc. all will improve your chances, but it all starts with pointing your finger at the target regardless of what else is happing around you and your body. in order of priority you need to see the exact center of the target( aim small, miss small)
You need to get your gun on target as fast as possible ( find the front sight), You need to make sure you are not the one shooting innocent bystanders( clear your background), from there you can build your chances by grip, breathing, trigger pull etc. etc. etc. These cowgirl/cowboy mounted shooters are able to do amazing marksmanship things from the back of a speeding horse. They are not able to control most things in their environment during the shoot, but they all see the target, get their front sight on it and engage multiple targets in a short amount of time.
My point: aim small, miss small (so your first attention is center of center mass), in a fight find your front sight (mental focus needs to cause your front sight and attention to center mass to be in aligned in your thought process), clear your background ( don't shoot the bystanders),and dry fire practice- it is not the quantity ( rounds per session) but the quality of your practice that is important
Just my thoughts on all the very useful information presented so far.