I shoot blackpowder firearms VERY often, doing cowboy action shooting. What I use to clean them, is Ballistol. You can get it at Midway, or Brownells, and probably at larger sporting stores.
If you use it straight it is a nice blackpowder friendly oil, that is non petroleum based. Thats very important, because any petroleum based oils tend to turn to a tar inside your gun, making cleanup a bear.
For cleaning, I mix about 1 part Ballistol to 7 parts water in a little spritz bottle. Ballistol will actually go into suspension in the water, making it look like milk. Then just spritz down the offending residue, and basically wipe off. Then oil with straight ballistol.
The nice part of this stuff, is that it is kind of like seasoning a cast iron skillet. The more you use it, the easier it seems to be to clean the firearms.