It takes me some time but I sight in with a clean barrel. Before my initial load, I swab the bore with a 50:50alcohol/windex(w/amonia) mixture. and dry patches.
On my flinters, I also wipe off the frizzen with carbuerator cleaner or other degreaser to remove any oil which may reduce spark.
If I do need a second shot in the field, and because I normally am using black powder, depending on what rifle I am using, I run a spit patch down the bore and a dry patch. I am fortunate that a couple of my rifles do not show much preference between clean and fouled barrel.