Despite the name, I think the bullet diameter is about the same as a 45 Colt- about .452 Try a 45 bore brush, and see how it fits. Pistol brushes are usually shorter than rifle brushes, since revolvers have to be cleaned from the muzzle, and the opening for the cylinder is not long enough to push a rifle brush completely OUT of the bore- reversing a brush while still in the bore ruins one quickly.
Jacketed bullets will likely not require a lot of hard cleaning- little powder solvent, wipe down, don't forget UNDER the extractor. LEAD bullets may start leading bore, requiring more energetic cleaning with a brush.
Clean cylinder from breech end, couple of passes with solvent soaked brush, let set a few minutes, dry patches. Use q tips to get space between cylinder and crane.
What we have heah is.... failure to communicate.