I prime the pan just like I would load a modern rifle, Starting time, load pan, nice day just check upon occasion, damp day check and change as needed, rainy day I don't lift my leather flap cover to check unless I can get under cover, always seem to get a rain drop square in the pan otherwise.
I unprime, flip the frizzen up and lay the hammer down on a dry patch before crossing fence, log, slippery bank etc same as unloading a modern rifle. With precussion I remove the cap and set the hammer down on a dry patch covering the nipple.
As Loggy said even an unprimed flinter can fire if a spark dances into the touch hole.