Good advice; FWIW - your rifle is a hook breech. For my hook breech GPR, I pop the barrel out, remove the nipple and drop the breech end in HOT water with (as MC One Shot says) plain ole dish soap in it. Then start swabbing the bore, keep the breech end in there and it will hydraulic the water right up to the muzzle. Swab it good; then take it out & a couple of good patches until they come out dry. Then all I do is run a patch of whatever gun oil I have handy down it. That's it, I don't have time to go back, no rust so far in ~25 years.
Then wipe out the lock if it needs it, the hammer for sure and any other part that got sooty. Done - put it back together; make sure the nipple & channel is clear if it's a percussion. You can do that by snapping a cap at a blade of grass or paper towel etc., watch for movement.
Some folks caution against the HOT water because of a risk of flash rust; I've never had it happen & it may be specific to your local humidity/conditions.
A critical part of your accuracy AND cleanup (and the time between needing to clean the barrel) is the patch lube. I've tried everything over the years from commercial stuff to chewing the patches; and everything in between. Chewing works OK but I found it just didn't hold up to many rounds, especially in hot weather - now I use nothing more than olive oil & water that's it that's all. I've shot as many as 50 rounds without cleaning the barrel, still ringing the gong. YMMV.
My 0.02 is all that is, worth what you paid for it.
Good luck; keep yer powder dry.