Normally if I get a flash in the pan without the main charge firing I will run the vent pick thru the touch hole to poke a hole into the powder charge.
In 99 percent of the cases this allows the next prime flash to fire the gun.
In these cases the vent pick is pushing aside any fouling that may have gotten into the hole and at the same time it creates a hole into the powder charge.
This hole will expose many more granules of powder to the heat of the pan flash than the few that are just at the mouth of the hole.
To visualize this imagine a bucket of damp sand with a board laying on it. The board has a 1/2 inch hole in it.
Shining a flashlight thru the hole will only light up the ones visible thru the hole.
Now, if a tapered rod is stuck down thru the hole and withdrawn and the light is again pointed thru the hole, many more grains of sand on the walls of the tapered cavity created by the rod will be illuminated.
The more grains of powder exposed to the pan flash, the greater the chances of the charge igniting.
Getting back to the flintlock, IMO, picking the vent hole after ramming the ball/bullet will increase the chances of the powder firing when the pan flashes.
This can be important for hunters to remember.
If the flintlock has the vent directly in the side of the barrel and there is no powder chamber or torturous path from the barrel to the vent hole, using M.D.'s method of sticking the vent pick into the hole before loading works well.
If the gun is like many of the factory made guns which have a small (1/8" or so) connecting hole between the bore and the vent hole, powder needs to be blown back thru this hole until it comes to rest just inside the vent.
If the vent hole is left unobstructed, loading the ball/bullet will force the air in the barrel out thru the vent, blowing the loose powder in the main charge down thru this hole to the vent hole.
If the vent hole is plugged with a vent pick, the air under the ball/bullet will be greatly restricted so the amount of powder blown down thru the connecting hole will be greatly decreased. This can lead to mis-fires.