Paper cartridges for the muzzle loading shotgun is a good way to load.
You can make a powder, wad & shot column....or easier, just a paper cylinder containing the shotcharge. Load powder from flask, add wad, shot-cylinder (paper, containing shot) & the overpowder wad. When shooting a lot, spritz some cleaning solvent down the bore after loading to keep fouling soft.
I really like stages having only two shots of shotgun anyway....whether muzzle -loaded or not.
Also like having an all-shotgun stage for our club's annual match, good way to mix it up.
Slim