I do not normally admit to owning any BP guns, someone might ask me to go shoot one and I do hate to clean the nasty things. Any way, here goes on the tips and tricks trail.
I learned from a Ned Roberts match shooter and whent a couple of times to the Ned Roberts matches in New Hampshire to watch the pros handle their tack drivers. The match shooter's gun was a 45 cal underhammer slug gun with a 1 1/4 across the flats heavy barrel, on wheels. I watched him shoot bowling pins with the gun at 175 yards, using patched balls.
1) If you want the best accuracy in a 45 use FFF black powder.
2) Increase the load until the report turns into a solid crack, sounding like a 30-06. Usually this is around 100 grains.
3) A patched ball is very accurate at 100 yards in a 45. Use precut pillow ticking patches soaked in Crisco or other lube such as water pump greese.
4) Between shots swab the bore using a heavy swab soaked with rubbing alcohol. It cleans / dissolves the crud and evaporates almost instantly. No dry patch is needed.
5) Use empty straight wall cartridge cases for a powder measure. Example, a 45-70 case holds 80 grains of FFF as I recall. Just put duct tape around it marked with a magic marker.
6) With a conical bullet, for hunting, fill the base with modeling clay and it will not contaminate the powder like a soft lube will.
I have not used bore butter but I understand it does real well to keep the rust away. I have never used a sabot. I have used Pyrodex and do not like it.
Best,
Ed
PS: To keep the wrath of the lovely lady from biting your rump, wash out the bore in a 5gal bucket of soapy Dawn hot water out in the yard.