[Jack]

There are a bunch of solvents that chemically dissolve jacket fouling, as you referred to in the other thread.
I don't know of any bore solvent that dissolves lead, in a similar manner to the way copper solvents work. Except for the aforementioned mercury, which has some well known draw backs.
The abrasive methods do work on lead- and often on copper, too. Things like JB or Iosso bore paste with mild abrasive in them, the Lewis Lead Remover, or the scrub pad that PJ mentioned. The scrub pad works the same way as a Lewis Lead remover, just not in a nice neat package.
Using a chunk of a Lead Wipe Away cloth as a patch works, too- and that's as close as I'm aware of as a chemical means of removing lead.
The other option is an Outers Foul Out set up- electrolysis. That works quite well, but it's not a quick process- takes some setting up and then letting it work.
If there's a magic trick to get rid of lead fouling in a bore, I haven't found it yet.