http://www.tbullock.com/bpsg.html
I like to use the old powder dippers to measure black powder.
For 12ga. - 3 drams of 2F, nitro card, 1/2' filler wad, over shot card, 1 oz of shot.. I use my progressive press to drop shot and to make a star crimp with federal paper hulls. Shells come out real nice.
Get the Lyman Black Powder Handbook and Loading Manual. Gives load data, velocity, and PSI.