.44 or .36 cal?
For your first loads for .44, try 23 gr. BP or Pyrodex P, with paper or felt wad between powder and ball. You can later adjust powder charges up or down to further fine tune, but 1858's and Colts all work great with 23 gr.
For .36 cal. 17 - 20 gr. produce amazing accuracy for me.
Sure, you'll have to loads it up really hot a few times for the flame, thunder and recoil, but for accuracy at the range, the lighter loads perform the best.