The best methods I've found include the Lewis Lead Remover or Brownells "Double Tuff" bronze brushes.
A man who knows how to season his iron!It's like a cast iron skillet. You gotta get the exact right combination of slow heat(all day on a woodstove is NOT the same as cranking up a new range on high) ,slick arse pan,just the right amount of grease. Failure in anyone of these,and you gonna be scraping eggs off with an air chisel.
Hard to bear the Lewis Lead Remover!! I have used them for years. Just have to buy a few new screens every now and then. Buy once and need regret it.My Lewis lead removal hasn't been used in over 20 years. In that time I've put nearly 100,000 rounds of lead through my 45's, 38's and 41 mags.
Try this. Take a 9mm bronze brush and wrap it with several strands of ALL COPPER CHORE BOY pot scrubbers. Run that through your bore several times and the lead will come out. Critical that it be all copper, not copper washed steel. That stuff will score your bore horribly.