Although I am new to muzzleloading I am not new to shooting. And even though you sound very knowledgable and don't need the following info, I thought maybe someone reading the posts might get something from it.
I used to be into competing big time. I did a lot of high power and big bore stuff at long range. Having said that, I have been to the range 5 times with my Lyman great plains 50Cal. I think alot of the basics stay the same even with the flash. In the military they teach BRAS. Breath, Relax, Aim, Squeeze. With this technique, be extremely focused on your front sight. Your rear sight should be in view just enough to make sure the front sight is seated correctly in the notch, but the focus on the front sight has to be sharp as can be. While focused on the front sight you will notice it moves in a triange in cadance with your breating. Pay attention to where you front sight is in relation to your target at the point of your exhale. You are at you most still point at the end of your exhale just before the transition to your inhale (Don't hold your breathe however! you will shake) Let the round fly at the exhale where your triangle is at the point of center mass on your target. Your view of the target should be blurry your view of the front sight should be crystal clear.
(don't mistake this for proper target identification!! Always ID your target before your train the barrel on it)
If you fear you may be flinching, load a charge in the pan, but do not load the barrel with anything. Place a dime on the end of your muzzle (or even better test, on the top of your front sight if it is filed flat enough. Octogon barrels are not as effective for this test as round barrels), take your position and squeeze. If the dime falls off the barrel you most likely are flinching. No one wants to use up flints and 4f powder on dry firing practice. You may want to try it with the flint removed and no powder.
Again, just a suggestion and some tips for those who may be interested. I have had very good results with my Lyman. Much better than I was hoping. I am consistently getting 3" groups at 100 yards. I do not know what would be required for getting into a competition but I am very happy with the consistency. Of course treating each shot exactly the same is very important for consistency. As an old habit, I clean the barrel very well after each shot and even let things cool down between shots. While hunting, your kill shot should be the only shot fired all day so if there no other shot to better predict you circumstances, make it your first cold shot. Always keep range data also. Man that is so important. You cant remember everything and humidity/temp/wind/clouds/sun/rain all plays an important part to the experience.
I know most kill shots are between 30 and 70 yards where extreme accuracy is not completely essential. But, I really enjoy getting to know exactly how my rifle will react in any given situation. With all the nutty things and nutty people there are in this world, (Michigan for example) you never know how accurate you may have to be!
I plan on doing a lot of ballistic work with my Lyman. I will post as much of my findings when feasible, but attaining consistency is really on the part the each individual shooter.