Some minor points.
As you are bringing the pistol up to aim, roll your wrist so that the priming powder falls to the outside of the pan, away from the vent. This helps to ensure that the flash has a clear path.
Also, if you are interested in match accuracy, get a primer. It's a tiny powder flask that dispenses a small (and consistent) amount of powder directly into the pan.
Remember that with a flintlock, consistency is everything.