Depending on the powder, Triple Se7en or Pyrodex Rs a simple solution of soap and water or Windex will take that out. As for the nipple, I soak them in Windex or some other such solution, even soap and water, and then with Q-tips clean the inside of the plug. A nipple pick will help clean the center. And then hit it with an air compressor to blow any water off. Then I like to pour pure alcohol through the breech plug, let that drain through, and then hit it with the air compressor one more time.