If you can, get rid of the Pyrodex and use real black powder. The fouling is much less corrosive.

Other than that, use a mop if you can find one that will scrub the bottom of the chambers - or a q-tip.

Don't hesitate to put this thing under the faucet to rinse as well as possible.

Finally, I find that with Pdex especially, it is worth running a patch the following morning as well

Brent