I leave the pan dry, and just close the frizzen on a toothpick. But, I am going to use the alcohol and patch technique the next time it rains on a hunt. You will have to go to a hardware or home supply store to find Denatured Alcohol. Drug stores carry rubbing alcohol, and isopropyl alcohol, both having a percentage of water in them. The 2 oz nasal spray bottle seems to be the best thing to carry in a pocket on a rainy day along with a couple of patches.
Don't worry about having to prime your pan when you see something coming. In the rain, deer move slowly, as the rain makes so much noise it interferes with their use o their ears as a primary defense sensor. You will have time to prime the pan. Use 3Fg or 2Fg, whatever you are putting down the barrel, for your prime. Don't bother to carry or try to use 4Fg powder. The coarser powders take on moisture slower than does priming powder. When you see a deer coming, just move behind your tree, if you are on the ground, prime the pan while taking a glance to see if the deer is staying on the same course, close the frizzen, cock the hammer, and mount the gun to your shoulder. swing the muzzle out around the tree trunk, to line up on the deer where you have a good shooting lane, and wait for the deer to get there. To prevent the " click " sound of cocking the hammer to full cock, just pull on the trigger and hold it back while you pull the hammer all the way back. Then, release the trigger, and then lower the hammer to the full cock notch. Very quiet way to get the job done.
Again the rain makes a lot of noise, so it is going to cover sounds you make, and the movement of trees, limbs, and leaves, if they are still on the trees, will also hide you, and any movement you make. The barrel of the gun, if its moved slowly, is going to look like a tree limb. Remember also that the deer have horrible depth perception because their eyes are located on the side of their heads, and not in front like yours. You have binocular vision. Prey species like deer do not. They react to any and all movement, because the only real defense they have is to run away- from anything that scares them. So, make all movements very slow. Hunting in the rain can be very productive, and you usually don't have to be out in the stuff before first light. Deer will often stay in the beds until 8 A.M. before leaving to feed. They want the light of the sun, and like all of us, they are a little bit optimistic that if they just wait, the skies will clear and the rain will stop.
, my oldest son did get 2 squirrels because our late flintlock runs with small game. 
