Since patched round balls won't leave lead in the bore, it's best to leave the brass brush in a sub caliber to use to clean out a chambered breech. Brass brushes work best in one direction. Reversing direction can put a lot of strain on the threads of the bore brush or the compression fitting of some brushes. A brush that is basically the groove diameter is okay, but a small wad of all copper "Chore Boy" brand scrubber on an undersized jag will work better. Boiling water will also loosen lead. The heat from the boiling water causes the lead to expand at a different rate than the steel of the barrel, loosening the lead and then the lead is pulled out with a normal cleaning patch.
Best to avoid brushing the barrel. There are some who use a bore brush and swear by them. There are others who use the bore brush and start a 20 page topic about how to remove a lost bore brush from my barrel.