You would need a metal brush for use in a bore with leading - not ever a problem with cap & revolvers in normal use.
A nylon bristle brush works well for removing any accumulated crud in the cylinder chambers, and a .22 cal nylon brush works great in the threaded cylinder nipple holes.
Otherwise, I just use hot soapy water and cloth patches in the bore, and a toothbrush for around the hammer face and cylinder recesses.