For removing leading from cylinder chambers, I chuck a bronze brush, damp with a bit of Hoppes No. 9, into a cordless drill.
30 seconds at medium speed, with a tight bore brush, removes it. I use .25 caliber brushes in .22, .35 in .32, .40 in .35 (.38, .357) and .50 in .44/45.
I would never use a steel brush in a steel chamber, for fear of removing chamber metal and changing chamber dimensions over time, but bronze brushes will wear before the steel chamber does.
For barrels, I use Iosso bore cleaner. It's a paste that comes in a tube. Alas, I ran out last week and didn't save the tube, so I can't recall if that's the real name.
Best stuff I've found.
If I can't find Iosso -- and it's harder and harder to find anymore -- I use JB Non-Embedding Bore Cleaning Compound. Comes in a small, screw-top tub.
With either Iosso or JB I put some on a clean patch, work it well into the fabric, then put the patch over the flat end of a length of wooden dowel that fits loosely in the bore.
Should be such a tight fit that you have to tap the dowel/patch combination down the bore.
When the patch emerges, it will carry with it long ribbons of lead it's picked up along the way.
A couple of treatments like this and most lead is gone and the bore gleams.
Follow this treatment with a a couple patches damp with Hoppes 9 to remove any paste residue.
This treatment will remove lead and fouling you can't even see.
Years ago, I was given a Marlin 410 lever-action shotgun. Built on the Model 93 action, it dated to 1929.
Lots of work with a bronze brush and Hoppes 9 left the bore bright and shiny.
Then I gave it the tight patch/Iosso treatment.
Wow!
Streaks of brown (rust) and black (lead) on the patch told me it was far from clean. My eyes had lied to me!
A couple more treatments of a tight patch on a cleaning rod, working it back and forth with the Iosso, left the bore sparkling.
Iosso is good stuff. If you find a tube of it, buy two; it's hard to find.