I shoot black powder in a Navy/Uberti Schofield as well as a Russian model. The Russian (in .44 Russian) functions just fine--I shoot 205g bullets with large grease grooves from a Saaco mould over a case full of Elephant 2F and have no problems.
The Schofield is a tougher customer. Large grease groove bullets (Lyman mould) don't carry enough lube, nor does the use of a single grease cookie over a wax paper wad (50-50 beeswax and olive oil) do the trick, at least not with .45 Colt loads. The following techniques have been more successful.
My best success is a slightly compressed load of Elephant 2F in a .45 Colt case (I compress it just enough to give a nice flat surface to seat the wads on and keep powder in place if I knock the cases over while reloading), with a pure beeswax wad about 1/16th of an inch thick on top of the powder, and a 1/8th inch thick grease cookie of 50-50 beeswax/olive oil on top of that, all topped off by a 250-grain RNFP.
The other load, which is a little easier for me to make (on account of how brittle the beeswax sheets are and what a pain they are for me to make) is a slightly compressed load of Elephant 2F, with a wax paper wad on top of the powder, and two 1/8th inch beeswax/olive oil wads on top of that, followed by the bullet. Oddly, despite the extra grease, this load tends to bind up after fewer rounds than the first load listed. I suspect that might be because of the ash from the wax paper.
With either load, I can shoot three or four stages with no problem, but I always make sure the cylinder spins freely at the unloading table. If it's gummy, I first try to oil it with whatever BP solvent/cleaner I have with me and wipe off the gunk. If it still sticks, I pull and regrease the cylinder. The one time I tried to go six stages with a Schofield without cleaning/greasing, I had to turn the cylinder by hand in the sixth stage--slows things down considerably. By contrast, my Russian model can go six stages with about zero maintenance except maybe a wipedown and a little solvent on the cylinder pin and cylinder face.
Your mileage may vary.