I start by un-breeching the barrel. If it has a drum, often it is threaded into the breech plug and it must be removed first. Next, I start with a loose-fitting jag- green scotchbrite combination with the barrel saturated with any water-soluble solvent like WD-40. Expect to ruin a lot of scotchbrite. Sometimes I’ll plug the barrel and drum and fill it with solvent to loosen things up. After I get to where I can pass a scotchbrite patch without shredding it and things are not muddy I take a look. Then decisions are made on whether I will re-cut the rifling.