Another vote for the alcohol clean-out before shooting. If it's a hooked breech, I will remove the barrel and nipple, then pour a little alcohol down the barrel, then I pump the bore with a cleaning patch to blow the alcohol out of the flash channel, then keep pumping to dry everything out. When I put the barrel and nipple back on, I pop a cap just to make sure. With a non-hooked breech, almost the same technique, except I put a patch over the nipple hole and let the hammer down to hold it in place. This keeps the alcohol from blowing all over the gun.
Or, you can remove the barrel and give it a quick clean with soapy water, pumping it through the flash channel, then dry noramally with patches, then hold the breech area over a heat source to evaporate any moisture still trapped in the breech. Again, pop a cap or two to make sure you got all the moisture. Bill