Rem Oil and bp
I'm a big user of Rem Oil. I hose my pistols down liberally before storage, and when I get them out I only swab the cylinder out with a Q-tip and alcohol before taking to range, just to make sure powder doesn't get wet by oil. It doesn't seem to bother the nipple. I used to clean it with alcohol and short piece of pipe cleaner before firing too, but it didn't seem to matter. I have never had a misfire. But bore and frame, recoil shield, loading lever and plunger are all left with a film of Rem Oil and when I finish up at the end of the day, Windex (or generic) takes everything off easily, then after drying it, the Rem Oil goes back on.
I don't spray it after it has any bp residue on it though. Only on a clean pistol.