CVA "Hawken" used a .22 caliber hole in the nipple drum for a long time. The drum is threaded the full width of the bore, seated and the hole drilled. A 22 cal brush works reasonably well but hot water flushing is better.
My wife does. I built it from a kit for her and fancied it up some with a checkered grip and some wire inlay. The LGS owner and I were good friends, good enough that I got my guns at cost and I wood fix things for him for free. He would go through the kits when he got them in and put back the ones with nice wood for good customers and I got the best one of the bunch when I bought the kit so it has very nice wood.
It has had very good care over the years and I have never had to repair anything.
Pics or it didn't happen.
With soap works well. The frizzen spring broke on the very first shot i fired. Bad luck. 1970sflushing (w/hot water) is the best way to clean a barrel.