Casting bullets and shooting black powder is a big adventure for sure. I have working on loads for my 45-70 Rolling Block and 45-70 Sharps for about 6 months and got them figured out pretty well. I am working on shooting off-hand and that is a bir harder than an AR-15 or even an M1 as there is nothing to really grab onto plus both guns weigh right at 12 lbs. To cast for black powder you would want soft (pure) lead so the bullet will obturate and seal the barrel as it travels to the crown. To help seal the bullet a good soft lube is best also. A very good source is roofing lead or isotope lead or sinker lead as they are nearly pure. Linotype is hard and many use 1lb of linotype to 5lbs of pure for rifles. For handguns such as wadcutter bullets, wheel weights will work but they are getting hard to find.
If you want to buy black powder, Coonies in Hobbs New Mexico is the best that most of the shooters I know of in the San Diego deal with. You have to buy a case but at 70 to 90gns a shot, a pound will disappear quickly! It is shipped UPS ground. For cleaning, I have found black powder easier to deal with than smokeless as long as I blow into the barrel after each shoot to keep the fouling soft. As for safety, black powder is no more of a hazard than smokeless so keep it locked up away from kids, heat, fire, etc. Here is a link showing a static electricity test as I had heard lost of talk about static electricity blowing us up....
http://www.ctmuzzleloaders.com/ctml_experiments/sparks/sparks.html
Probably the best website for casting is:
Cast Boolits - Dedicated To The World Of Cast Bullets!
and you will see forums for everything remotely associated with casting. Good luck