I think I'd try either regular Black Powder (FFFg) or Clear Shot...Do NOT try Clean Shot. I have heard that it really attacks brass, and I have not tried to check this. Pyrodex can be a real pain, so the regular BP or Clear Shot (very expen$ive...abt $30/lb.) should work fine. You'll just have to be more careful about cleaning regular BP, since it's corrosive (Clear Shot isn't).
The standard technique for loading cartridges with BP (or any substitute) is to fill the case with enough powder to require slight (at least) compression before you can seat the bullet. Upon NO account leave an air gap between the powder and the bullet base. The compression is usually applied before the bullet is seated, by means of a compression rod that takes the place of the bullet seater in the die. It is wise at this time to seat at the same time a thin card wad to prevent 1) the powder getting buggered up by the bullet lube, and 2) the flame of the powder from messing up the bullet base. The bullet is cast and lubricated with a good BP lube (such as SPG). There must be sufficient big lube grooves to hold enough lube to make a nice "lube star" on the muzzle. The purpose of the lube is not so much making things slippery as to keep the BP fouling soft. If it dries and gets hard, lead (Pb) will be deposited in the barrel, and you definitely will not like that.
A good, firm crimp should be applied, to keep the revolver from tying up when the bullets shift forward in recoil.
It's really very simple, and it's a whole lot more fun than smokeless powder! I've never seen a newbie shoot a BP weapon for the first time that he didn't leave smiling.