Char, don't even think about smokeless powder, PERIOD.
If you want to try something different than blackpowder, and easier to clean, try Pyrodex or Trip 7 or any of the other "Black Powder Substitutes" you find at Walmart or just about anywhere. Read the labels, and look for the ones that say "fffG" or equivalent. Some even come in pre-measured "pellets' that make it even easier.
Now as for a wad or filler, I don't use any. I use 25 gr. of fffG BP and seat the .452 ball or conical over it, it seats really tight, even shaves a little ring of lead off of them. Then I fill the cylinder with a dab of CVA cylinder grease (that looks, feels and smells a LOT like "Crisco"
) and fire away.
My revolver is a "Traditions" 1860 Army that takes .452 balls or bullets, which conveniently is the diameter my .45 acp 200 grain lead SWCs are, so I shoot them through it quite a bit since I have thousands left over from my IPSC days....they can be tricky and a little slow to load straight, because the rammer head is concave and these are flat nosed, but when loaded they shoot fine, although they recoil a little harder...I shoot them with only about 20 grains of powder though, to make sure the longer bullet will seat below the cylinder mouth...
I get my roundballs and conicals from a guy at the Indy 1500 gun show that casts them, I paid about 6 months ago if I remember right like $3.50/100 for roundballs, and like $6/100 for conicals....
As for leather, I used to dabble with making leather stuff when I was more involved with the NMLRA and the Rendezvous' there twice a year, the first holster I ever attempted I made about 15 years ago or so with leather scraps I got at Friendship. and while it wasn't perfect, it works, and the Traditions is hanging from the gun rack in that holster as we speak! I call it my "Polish/Mexican Tie down Model."