smoothshooter
50 Cal.
As others have said, remove lock, plug touchhole, add water (maybe with a little dishsoap but that's another topic), maybe slosh it back and forth a bit with a cork in the muzzle, dump and repeat, swab a bit of really dirty, repeat process with clean water,,,, swab dry, add bore protectant of your choice (again, a whole other, and often contentious, topic).
Sometimes one encounters a touchhole that just won't seal.
In that case,
https://www.muzzleloadingforum.com/threads/finally-a-flintlock-flush-kit-that-really-works.162338/
70% isopropyl alcohol is my preferred liquid for cleaning the bore. It does require running a couple of oily patches up and down the bore after the alcohol evaporates.
Diluted Balistol works well too.