Callouses will come much faster playing the medium gauge strings on an acoustic than super slinkies on an electric. If you have both, play both and you're electric will feel easier. Play songs you like with authority. Practicing scales is not likely to draw you into the pressure of really swinging with songs you enjoy (not to say don't practice scales at all). Use coated strings. They are "faster" because they cut down on squeak. And the friction from the squeak can be a little painful compared to the sleekness of good coateds. I find Elixir Nanowebs perfect whereas I found Martin's coated strings a few years back gunky and primitive. That may have changed though.