Turpentine..............
Certainly worth a try.
Provided that it can actually be found anywhere. Haven't bought any in years. Used it in the past for cleaning paint brushes; have since converted to petrol mineral spirits.
Bore leading is generally no big deal, given enough cycles on the brass brush.
However, external surface lead is really tough to remove from my S&W Model 19. Got some on barrel at the muzzle. Some on front end of cylinder. I've since switched from bare lead wadcutters to Berrysbullets plated wadcutters.
So far, the only solvent I've found that halfway works for lead removal is hydrogen peroxide/vinegar, 50-50. However, it also does a nice job of removing bluing from handguns.
I'll try turpentine and let you know.
Ken