I have the stainless Kodiak 50 cal (can hold a 150 charge in pellet, maybe 130 in powder but generally cruise around 100+/-) and use Powerbelts with triple seven powder and triple seven 209 primers. I'm not into the real traditional black powder. I like being able to access the breach and removing the plug to dump my powder as a just in case as opposed to bullet pulling with a charge behind in. I like using powder over pellets as I can get a really sweet load up as where I've only seen (not really looked) the pellets in 50 and 30 grain. I don't know how new to black powder you are but grain is not weight in black powder shooting, it's volume, as opposed to weight in smokeless powder. You can purchase bullet starters with multiple heads for different shaped shot. They usually come with 9 in groups of three. 2 for the long and short ends of the starter and one for the ram rod, along with a cleaning jag, bullet puller and patch remove it in case you lose it in the barrel. I have an extra fiberglass ram rod for the range that's extra long and marked for proper seating. I never use the one on the rifle except in the field. What also helps your mitt is getting a ball grip for your ram rod. It's just a ball with a hole in it that you put over the end of the ram rod for seating. Don't forget all the other stuff if you go like cleaning patches and solution for use after every shot. A quick swabbing will let you go all day long and all day for me is like 20 shots. If not, each successive shot gets harder to seat.
EDTA: Don't use anything but water base solvents in your internals. It's okay to use oils and stuff lightly on the outside to preserve the metal after you clean it with water base but not the inside. And clean it as soon as you can. All black powder is corrosive. I also like to fire a couple of primers off before the first loading.