Also, if you can find it, "The .50-70 shooters handbook" by Croft Barker is a fine read.
For smokeless, I load 28 grains of 5744 under the Government 450 grain bullet (Lee Mold) But BP clean up of my .50-70 carbine is so easy I rarely bother. I have a rolling block in .43 Spanish I treat the same way after a BP session: stick a kitchen funnel in the breach, pour a cup of water down the barrel, a couple of dry patch's and a Ballistol patch, and put it away.