A bronze brush works--but, as Mad Magyar mentioned, a nylon brush will also do wonders and will reduce almost completely any chance of scoring the cylinder bores.
Some tips:
1. Hoppe's works fine for this purpose. I recommend that you get a large bottle and a small glass wide mouth jar. Dip your brush in some solvent in the wide mouth jar--do not contaminate your main bottle of solvent.
2. Do this outside, or over a BUNCH of newspaper. Don't ask me how I know--just say that my wife reminded me, VERY stridently.
3. Use a 3/8" VSR drill. Run it at slow speed, it will do the trick. Remember to run the drill both on insertion and extraction. Working the brush back and forth slightly will speed the job.
4. I recommend the use of TWO brushes--one for solvent, and after you're done with it use the clean brush with a thick patch wrapped around it. Cleans out all the gunk really well when this is done. BTW, I recommend the mil-spec patches available from Brownell's--they work amazingly well.
5. Get long bore brushes. You can drip some solvent on it and lay it across the cylinder face. Run the drill at slow speed and it will do a bang up job of removing fouling from the cylinder face. Of course, the lead removal cloths will do it too--but don't use them on blued revolvers!!
Remember to check under the extractor star when you're done. Amazing amounts of crud will find its way under there, and will cause problems.
Good luck!