Here's another input. I also started this addiction in the 70's. At the time, there wasn't much info to pick from, so Dixie Gun Works mostly supplied everything. In the back of a catalog there was the tip of pouring powder on a ball. When the ball was covered, that was the "right" amount. You could take that amount and make you measure to hold it. Since most muzzleloaders don't have a selector switch to flip it to "Rock and Roll", you had to hit what you wanted on the first shot, so having loads that are exactly the same is of great importance. On the run, it was really pot-luck. Pouring powder into a sweaty hand would be a really big mistake, and a measure would be to much to handle. If you're chasing someone, stop and load it right. If someone is chasing you, well, you're going to have to throw lead any way you can.
Also, you have to remember that most of the Mountain Men and those prior, could teach all of us a thing or two about Bull Sh*ting so you have to take that into account.