I've always used acetone and it's worked well.
I suspect carb cleaner will as well.
I use a worn cleaning brush and wrap it with some steel wool. Then saturate the steel wool with the acetone. The wool holds the liquid well so it doesn't spill all over.
But some will be squeezed out anyway as you work it into the bore and back and forth.
So have some cardboard or paper on the floor to absorb it.
Keep any of these solvents away from the wood / wood finish of course. Also any synthetic/plastic fittings (including plastic sight beads) on the gun as it will most likely soften and start to dissolve it also.
The acetone will cut through the plastic fouling in the bbl easily dissolving it mostly and then allowing some of it to come out on the brush in pieces.
