I take the breech plug to the kitchen. Fill a coffee can with hot water and add a squirt of dish soap. Then all you do is take an old tooth brush and scrub the outside of the breech plug, a pipe cleaner for the indside, and if it a hollow based kind, rinse it in hot water, and the dip some Q-tips in solvent and scrub all parts of the breech plug you can get to..
After that make sure it is nice and dry.