Take a "Chore Boy" copper scrub pad apart. It is a tube. Use patches to fil the tube to snug bore fit. Tie long piece of twine on ends of tube. Use cleaning rod to run the twine through the bore. Grab twine and "shoe shine" to a bright bore in just minutes. 

The turpentine and tight patch will get most of the lead out in the lower edges of the grooves.

Interesting test on the internet using acetone and atf. Many swear it is a lot better than any penetrating oil. There are a number of posts saying it will not work. There are a number of posts who say use atf straight up. Swab the bore and let it set for so long and drive a patch(s) down the bore. How many of you have hammered a cleaning rod fitted with a jag and sufficient patches to be driven down the bore with a hammer. Dead blows are best.

If it beats Kroil and the others................

Acetone will not harm your blued steel. Keep it away from certain wood finishes. 

I've used turpentine and a very tight brush which works fine if the leading is not real heavy.  But nothing works better than the Foul Out electrochemical bore cleaner.  It was discontinued several years ago due to misuse by shooters leaving it on overnight or unattended for many hours.  As long as the instructions are followed nothing works better.  They can be found on eBay now and then.  Here's a brand new one listed now:
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Wayne

MPro-7
I had a S&W stainless .38 spl revolver that though used had been shot very little.  First time I shot it with lead semi wadcutter it leaded badly. I could not get the lead to budge.
A fellow suggested MPro-7, and when used according to the instructions I got chunks of lead out of the barrel. It worked it's way between the barrel and the leading a d broke it loose.
Great product.

As Wayne points out the Foul-out system was by far the best and like you say would still be available except a few boneheads unable to follow directions scared them off. It was an electrolyte filled barrel, a cathode and anode some regulated small voltage that generated a reverse plating or electro-plating operation. When done the bore was incredibly clean.

Steel wool and Hoppes #9.

Try High School chemistry teacher,  (OLD)Dentist , Miner's
LD1

The modern lead solvents actually  do a pretty good job, I use boretech rimfire blend and their chameleon gel.  Beats hoppe, less dangerous to the barrel than steel wool...

Since turpentine is not an option for you, for really heavy lead, the next best thing to the Foul Out unit I've found is wrapping some copper scouring pad around a tight patch.  Copper scouring pads are available at your local grocer store or on Amazon.
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Wayne