Pull the barrel (no big deal) and drop the vent end into a pot of hot water w/ a drop of liquid dish soap. Use a reasonably tight patch** to
geeeently pump some soapy water in/out of the bottom of the barrel/vent (melt/dissolve any "bore butter").
From this point on, don't use bore butter or anything like it. If you patch the ball, use a
lightly dampened "spit" patch -- nothing more.
Use a damp spit patch to cleaning between shots too. Nothing more.
Get a 75-caliber one of these and use it at the end of each shooting session
https://www.trackofthewolf.com/list/Item.aspx/579/1 ***
If you don't already have it, get this (or a) non-rotating steel rod and **put a true 75-cal jag on it so as not to lose a patch down the barrel. This rod will also let you twist the scraper.
https://www.trackofthewolf.com/Categories/PartDetail.aspx/566/1/RAMROD-C-29-10
(but get one of these anyway...)
https://www.trackofthewolf.com/Categories/PartDetail.aspx/179/1/WORM-CORK-10
You may already have this stuff and I'm preaching to a well-experienced choir...
...but it not, they save a
lotta headache.
***Turn the barrel upside down after shooting and
before putting any solvent/moose milk in it to clean the bore. Use the scraper to scrape the
dry crud from the breech and it will fall out the muzzle like charcoal rain. Then you can clean normally. (Note: you can also put a patch over the end/on the scraper after that and it
really cleans things up)