Sure do. With either Red Dot or Bullseye, around 4 to 5 grains should easily do it. Maybe less. If you fill the case with polyester pillow stuffing (dacron) after putting in the powder, it helps clean the bore and you can use less powder. By "fill the case with dacron" I mean stuff as much as you can in there. Probably will end up with 10-12 grains of Dacron on top of the powder, if you get ambitious and weigh the stuff.
I wouldn't go any slower than some thing like Unique, and I'm not 100% how it would work.
I haven't lapped a .45-70, but have done many different rifles in that case range. As an example the .444 Marlin will put lapping loads out the barrel at around 3 grains of Bullseye, with the rest of the case stuffed full of Dacron.
Good luck. Be prepared to stick a bullet or two, it happens. Make sure each one exits the barrel. Don't try to use the brass for anything else when done, it will be contaminated with abrasive.