My brother, Sawyer, SASS#32450 and I have been reloading BP shotgun shells since we started CAS. I buy wads and cards from
http://www.circlefly.com You can get the fiber wads dry or treated with something like Bore Butter, not sure what they actually use. I've tried a lot of different recipies, but am about to settle on this:
Lee 7/8ths ounce shot dipper of Pyrodex RS, an overpowder card, two 1/2 inch fiber wads, a 7/8ths dipper of shot, enough corn meal to finish filling the hull, and an overshot card. I use this load for 10, 12 and 16 gauge. I know I could make a much heavier load, but corn meal is much cheaper than lead.
Sawyer, on the other hand, likes bigger booms. He's loaded his 10 gauge with as much as 200 grains of Elephant FFg just to raise the roof on some of the stages where he shoots.
I know my 10 gauge load would be considered light for even a 20 gauge, but my gun is like me. Old and needs to start slow and work up.