After I remove the nipple, I like to take a pipe cleaner ( get the white ones at the Dollar Store) and dip that into solvent. That pipe cleaner will slide right into the nipple port and you can then scratch around in there and make sure there is no fowling. Use the other end dipped in isopropyl alcohol and that will make sure it is nice and dry, after a water bath. Then take a Q-tip dipped in alcohol and push that in there and scrub the threads where the nipple goes. Make sure there is no fowling there. The last thing you want to corrode is the threads of the bolster because a nipple canl come loose and fly out from back pressure when you fire,should the threads wear away from rust and use.