You could go the paper patch route. For a .458" bore you use bullets that are .448" to .452" and paper patch them up to .459"-.460". You can try using 300gr .452" bullets meant for a .45 Colt to try it out and see if it's for you. Black powder cartridge shooting really is a labour of love since smokeless is just so much easier and less messy.
You load black powder in the case, put a thin fibre wad over the powder, melt and pour in a small measured quantity of black powder lube (a fired small handgun case usually works as a dipper/measure), and are good to go. Whether the bullet under the paper patch has black powder lube, smokeless lube, or no lube at all doesn't matter.
This video has a pretty good introduction to it. Different cartridge