Period correct would be to use a fixed powder measure made from brass/copper. A modern adjustable powder measure is not correct. Of course you need to use a powder horn.

Some of the guns in the old days came with the proper powder measure. Of course a speedloader is the fastest, and you don't need a powder horn. You can also make period correct speedloaders. Hammer them out of copper, and put a cork in them.

Anything you can think of now. You could have thought of back then too. Use your imagination, and don't use modern materials. It's all part of the fun, and you only need to satisfy yourself.