I used a 10 ga with BP for several years in Cowboy shooting, it was a hoot! Typical 2-7/8" 10 ga shells back in the day were loaded with 1-/1/4 to 1-1/2 oz of shot and 3-1/4 to 3-3/4 drams of black. I usually loaded 1-1/8 oz shot and a bit over 3 drams (90 grains) of FFg, basically a standard 12 gauge load, filling the space inside the cases with fiber wads. You can certainly load more, but that much BP will definitely buck and roar plenty!
Plastic wads with black powder make some of the most disgusting gunk you will ever see thoroughly stuck all through your barrels, ask me how I know...
I used Federal plastic hulls before I had some turned brass ones made; the Federals would get holes burned through them with only one or two uses. If you are using thin wall brass hulls like the Magtech ones you will need 9 gauge wads; those are available at Track of the Wolf.