I haven't been shooting a flintlock for many years, and fight a flinch. I find it helps to watch where the sights are when the gun recoils. If you can see the gun recoiling off the target, and know where the sigths were linded up as recoil started, you know you didn't flinch. If you dont' see the gun recoil and rise, you shut your eye - or eyes.
My flint lock shooting mentor insisted that I dryfire, with only a wooden block in the jaws of the cock, for a minimum of 15 minutes a day, off hand, every day for a full month. He then insisted that I flash powder in the pan, for at least 15 minutes a day, every day for a full month. I then progressed to shooting reduced loads, of 30 gr of powder in a 54 rifle, at short range, for at least 15 minutes a day, every day for a full month.
Though it was a difficult regimen to follow, I did pretty much, follow Crow's shooting routine for three months.
Two weeks after completing this training, I won third place in a field of nearly 150 competitors.
My "friends," who scoffed at my desire to shoot a flint gun, derisively encouraged me to enter that match. However, I beat 'em all...really badly, much to their shock and chagrin. They no longer laughed at my desire to shoot a flint gun after that day.
The key to GOOD practice is learning and applying the basics of good marksmanship that Randy offered, in addition to dedicating a specific time period, every day, or every week for GOOD practice.
I later learned that it takes a minimum of 40 hours of practice to develop good muscle memory. Three months of 15 minutes a day = only about 11 hours, but with continued practice, my scores continued to improve...and yours will too.
God Bless,
J.D.