RoyB,
Most of the folks who have responded already are target shooting so they have covered the basics.
I shoot a snug fitting bore diameter PP bullet all my rifles;
40 to 50 caliber. Wipe every shot with a damp patch or two. Keep the chamber dry to eliminate separated cases.
In my 40-70SS I use a lube wad so I only wipe once with a damp patch, which is good enough for gong matches. I may try a lube wad in my 50-70 carbine also.
If you were to lube the patched bullet paper, you may introduce grit into the bore, so I would not recommend lubed paper.
The alloy of choice will depend on the bullet profile and the caliber. Long slender nose on the bullet will require harder alloy. Heavy powder charges will also need harder alloy.
I have not tried smo*** powder with PP bullets, but if you use a quick enough powder, it should work OK.
One of these days I will get a round to trying a groove diameter PP bullet. Leave no stone un-turned.
Keep on hav'n fun!
MikeT