firstly, if the gun has been well maintained, there is no need for anything more than tepid tap water to dissolve bp residue.
again, LOTS will depend on how well the gun has been, or was, maintained.
what does "well maintained" mean?
it means to immediately attend to the bbl and lock after the last shot of the day is taken in order to prevent bp residue from getting crusty hard and/or eating the metal. after that last shot of the day, this is where i use my version of "moose milk", which is a 1:6 (or so) blend of ballistol:water. while it's really the water that does the bp dissolving, ballistol, or most any water soluble oil, is added to the water to protect both the metal and the wood. i run a few moose milk sloppy patches down the tube and
leave the last very wet patch (and rod) down the tube (important). then a small pump spray bottle filled with moose milk gets to spritz down the lock. in doing this pre-clean cleaning, the bp residue stays soft for the real cleaning when back at the ranch house.
failure to care for bp residue ASAP will more than likely mean chemicals and nasty concoctions will be required somewhere down the road, usually sooner than later. this makes the purveyors of all those fancy schmancy expensive muzzleloader cleaning potions both happy and rich.
for the real cleaning ...
remove the flint and its leather from the lock, then pull it off the gun and leave it dunked it in a bowl of tepid tap water. the bbl touch hole is plugged with a round toothpick and tepid tap water is poured down the barrel about 1/2 to 3/4 - there is no need for more water than that. leave the gun standing on its butt stock and go attend the lock.
the lock is scrubbed with an old stiff toothbrush, rinsed in clean water, patted mostly dry with a towel (cloth or paper), spritzed wet with either water soluble oil (any kind, i use ballistol) or wd40, patted mostly dry with a paper towel. then all the lock pivot points get a *tiny* drop of gun oil.
back to the tube, pull the toothpick and allow the bbl water to pizz out. a few patched jag passes down and out the tube, until a patch looks *reasonably* clean (
it will Never be perfectly clean, which is Correct). for me, this is 2 to 4 patches, rarely more. a few patches to dry the tube, and a final patch with gun oil i sent down to kiss the breech plug and left there.
screw back the lock, load the cock jaws with leathered flint, wipe down the entire gun - metal and wood - with a cotton rag that's very lightly damp with ballistol (or any water soluble oil). done.
before shooting the gun, run some dry patches down the tube to clear out any oil residue, wipe down the lock with a dry cotton cloth.
there now, wasn't that both easy and fun?!
NOTE: there will be an added step or three if the barrel employs a patent breech (this will be true for 99.9% of all offshore trad muzzleloaders).