Another thing you can do is leave your measure home when you're hunting, and carry your shot and powder in a sort of paper cartridge. Choked and tied off in the middle, powder in one end, shot in the other. This allows you to use some precision in measuring at home, and just "bite - tear - pour" when loading in the field. If you're shooting a flinter, you'll still need some sort of dispenser, or at least a container, for priming powder, but you can still carry everything for several shots just in the pockets of your jacket or vest.
Since these are not loaded into the gun, precision and uniformity in the paper tube is not required, just sufficient strength to carry around, so they're quick and easy to make. You can make up lots of empty tubes while you'e watching TV or listening to a game.
Find someting (a chunk of dowel or tubing, a magic-marker, etc.) a handy size to roll them around, then cut your paper wide enough to go around it a few times. Roll the tube up, glue the long edge, and set it aside to dry while you make the next one. When you've got enough glued up, take one, slip your dowel back in half way, pinch and twist the middle closed, and tie it off. Be careful to to tear it when you do this; a rounded end on your dowel (or whatever) makes this easier. Then do the next one.
I recomend filling them some time when you can concenterate a little more. You can fold the ends closed like a musket cartridge, or glue or tie them closed, but if you're not worried about authenticity, it's quick to just fold the ends over a couple of times and staple them.
If you use different loads, you might want to use a different colo(u)r or type of paper for each load, or write the basic load info on them, rather than just labelling the bag or box you store/carry them in.
Joel