After cleaning the gun and the flash channel, and the threads in both the bolster or patent breech, and the threads on the nipple, Always put a drop of oil on the threads of the nipple, and on the threads in the bolster where you screw the nipple into the action, so that you can more easily remove the nipple for maintenance the next time you finish shooting. Keep pipe cleaners in your kit to clean out the flash channel. On a new gun, take a drill bit that fits in the flash channel, and check to see there are no casting burrs, or crud in the flash channel. If there are, use a slow speed drill to open up the channel, and remove the obstructions. If you have them, go a couple of sizes larger in drill bits, and use the larger bit to open the flash channel larger. ( ie., if the channel is 1/16", use a 3/32" bit to widen it some.) Polish the channel smooth. This makes it easier to clean, and keep clean between shots, and widening the hole makes it much easier for the flash from your percussion cap to reach the powder and ignite it. If you shoot 3Fg powder in guns with flash channels, some of the powder will spill into the flash channel, speeding ignition but also leaving powder residue there which can take on moisture from the air. The larger the flash channel is, the less likely it is going to clog up so that the gun stops firing. In really hot, humid conditions, or on warm days when its raining, be prepared to dry out that flash channel with a pipe clean after ever 10-20 shots. That means you have to have a correct fitting screwdriver, and your nipple wrench with you when doing long bouts of shooting, but they should be in your range box along with other tools needed to take the gun apart for cleaning and maintenance, anyway.
Maintain the clean-out screw in your gun the same way you oil the nipple. It actually is subject to much more pressure when the gun fires, than the nipple is, and is more likely to become stuck.