Those old guns were built to use black powder, don't be afraid of it. If you have the brass, pick up a can of 1F or 2F and fill the case to just above where the base of the bullet will be, place a wad on top of the powder and have fun. Black is not hard to clean up after, gives good accuracy and is just fun to do things the old way.  I have 3 modern built rifles, a Shiloh, a custom Browning 78 and a rolling block, none of them have seen any smokeless powder and they are all good shooters. 
Over the weekend my rolling block had 40 rounds put through it, it was wiped between shots and then it sat till this morning. a few wet patches a couple of dry and an oily patch and it was nice and clean. Yes there was a bit of a carbon build up just infront of the chamber but the wet patches took care of that. Black will shoot well and is not hard to clean up after. 
As far as case care goes, a mix of vinigar and water will get the bulk of the fouling out of the cases and a little scrubing with soapy water will get the rest and then toss them in a vibrator with walnut hulls or corn cob will get the last of the junk out and they will be ready to go again. 
Its not like Star Wars, do not fear the dark side. Its not that bad.
Sam

You might try 27-29 grains (no wads - no fillers) of 5744 with the standard government bullet (Lyman 515141).