With a properly patched ball the lead never touches the bore so if you were getting lead fouling the patches must be shredding to bits in the bore. You should be able to pick up fired patches and they should look good enough to use again. You don't give us any info as to ball size and patch thickness and these are things you absolutely must know. For patches I mostly use pillow ticking, the striped cotton cloth from Walmart which mikes about .018" thickness and try never to use any patches thinner than .015" because thinner cloth is just too flimsy to withstand the stress of being rammed down and fired out of a gun. The first thing you need to do however is get the lead out. Wrap some medium coarse steel wool around a .30 caliber bore brush and scrub the lead out, it will take some serious scrubbing but work it until you no longer see those shiny flakes coming out.