Follow Dean's advice. All my bronze brushes have strands of a frontier pad wrapped around them. I also us G96 Gun Treatment (hard to find but exceptional cleaner) with the brushes. You just can't beat frontier pads, they will take everything out of your barrels and not harm them at all.

For stubborn leading in the bores the product I go to is Kano Kroil Penetrating Oil. It is also great for removing lead from rifled bores if you shoot lead bullets in pistols or rifles. The key is to give it time to soak to loosen the lead and brush the bore, and repeat. You'll see chunks of lead come out on the patch.

It is also great to have around the garage when you work on things to help loosen rusted hardware.

They sell this on Midway USA.

Kano is wonderful for removing lead. NRA Highpower shooters have been mixing it 50/50 with No. 9 for an even better bore cleaner. Back in the Nineties when moly coated bullets were all the rage it cut moly better than just about anything. All the service teams relied on it. I learned of this mixture at Camp Perry. You won't be sorry.