When sighting in, I always have a clean barrel, I swab between shots. Then I shot with a clean barrel followed up with a dirty barrel, and see if there is any difference. I do not make any corrections for my second shot, because I always hunt with a clean barrel and I know where it is. To tell you the truth, my Encore Pro-Hunter is at the same point of impact with the second shot as it is with the first with a clean bore. How luck can I get.
After a day at the range, I clean my M/L completely, because like I said, I know where my gun shoots on a clean barrel. I use Windex the Multi-suffice with vinegar to clean all my black powder guns. Works great, my buddy uses windshield wiper fluid. We both use break free after we run dry patches and then use bore butter to prevent corrosion. It was worked for me for many years without one problem.