It was drilling. Ensuring they followed the Tactical Drills and Musketry Drills, not just marching. It may have been the RESPONSIBILITY of the Commanding Officer - just as it is now - but it was the regular or ex-regular sergeants who conducted the training, just like FMJ, but with less in-your-face and Fs. You taught them the drills, then you did it over and over again until they got it right, then again and again until it was automatic. THREE rounds per minute, a load and ready in 20 SECONDS. No more.
A Major or Colonel would not conduct any training, just walk around to ensure it was being done. Nor would he allow any of his officers to do it! Far too much shouting and cussing! In any case, they needed training too!