I recently took a short class on stick welding. The instructor told us that if we're having trouble striking an arc, it sometimes helps to cuss at it. Amazingly, it helps sometimes.
But I think flintlocks are more sensitive. The more I cuss at it, the worse it behaves. Mine like me to be slow, patient, deliberate and consistent in my loading procedures before they give me any reliability. If I do everything just right, it will go off... Most of the time.
I'm no expert on flintlocks -- far from it. Definitely more of a newbie. But I own a Pedersoli Kentucky .50 and have both flint (original) and percussion locks for it. So I'm speaking from some experience with that particular gun, albeit still rather limited.
I really enjoy that rifle. At first, the flints were resting against the frizzen in half-cock. So I chipped the back of them so that they'd set back just a bit and saw MUCH better pan ignition. For both my Kentucky and my Trade Gun (also Pedersoli), the pan ignites the main charge best when I can see a grain or two of powder through the flash hole. I hear this usually creates a fuse effect, slowing ignition. But it has helped mine considerably. Mind you, there's still a gap between the priming charge and the main charge. But it's small. I can certainly create that fuse effect by cramming powder into the vent from the pan. And, yes, that stinks. But if I just let the powder settle down to where I can see it, it helps a ton -- prob 90% igition & fast too. Maybe it's a Pedersoli thing (chambered breach?). Maybe it's just my guns. Who knows? Probably best to start with the more common advice of just tapping the lock a few times and calling it good. If that fails, then experiment until you find something that works.
So, when loading, I start by wiping the frizzen, then the pan, then the underside of the flint & then clear the flash channel with a pick, assuming this isn't the first shot of the day. If it is the first shot, then I'll start by sparking the lock one time. Why? Don't know. It just works best if I click the lock once & see that spark before loading. Missed a turkey last year when the lock clicked & failed to ignite the main charge (trade gun). Never had that happen when I click the lock once -- always get ignition of the pan the first time, even in damp marshy conditions.
Only after doing those things do I pour the main charge in the barrel. Then I want to see a grain or two of powder through that vent & I'll rap the side of the lock until I see it. This is much easier with homemade powder since it's more gray than black & shows up easier in the dark hole of the vent. But even if I can't see commercial powder in the vent, I'll use the vent pick to feel for it. Then I'll load my patched ball, prime & close the frizzen.
One of the really nice things about the Pedersoli rifles is that you can usually swap back/forth from flint to percussion if you buy an extra lock for it. I think you can even buy a kentucky pistol and use the lock from that, or a couple other models. Mine came with a flintlock and I wasn't having much luck with it at first. I thought the rifle wasn't very accurate. But after putting a percussion lock on it, I found out that it wasn't the rifle's fault at all -- it was all me. The rifle is VERY accurate. I am the problem. With the percussion lock, I was then able to sight it in better & then switch back to a flintlock when I was ready to work on that skill again. For now, I only hunt with the Kentucky rifle with the percussion lock on it and I appreciate being able to choose how I want to use the rifle based on what I'm doing.
Be prepared for some frustrations and a learning curve. Some people seem to be able to pick one up and shoot it just fine without much fuss. I'm not one of those people. I still flinch -- even the slight delay of good ignition is enough for my brain to anticipate the recoil & move the sights. Recently, it took me about 5 shots to hit a beer can at only 25 yards and I rested on a tire for 3 of those shots. Meanwhile, with the percussion lock, I can hit a 10" gong at 90 yards from a seated position most of the time so I know it's just the flintlock. Hope you have an easier time with it. Or, maybe, I hope you enjoy the challenge. As my son once told me, "It's fun to hit something with a .22. But it's fun with a flintlock whether I hit it or not."