No more of a pain than any other.
Even in traditional style BP rifles there can be variations.
Plain hot soapy water works as well as anything.
Personally I use plain rubbing alcohol.
Mine is a 30 yr old CVA plains rifle. On mine
I can remove the bolster / drum cleanout screw, the nipple
and the drum itself. to really clean the chamber area.
Mine is a .50 cal. I use a .410 gauge and 12 gauge bore brush
and then cotton flannel shirts to swab.
I'm cheap. So I save my cotton flannel patches cut from the shirt,
put them in a sock and wash them and reuse them a couple times.
I dry swab clean.
I roll paper cartridges, I reload the gun. Then a lightly oiled patch down the bore to the ball.
Place on gun rack with my capper hanging from the nipple ready to go.