I really like the Pochmann-Method for centers, you almost never have to look around the cube, I average about 20-25 seconds without much practice, it's very fast if you use the tips given on the bottom of the page:
http://www.stefan-pochmann.info/spocc/speedsolving/4x4_centers/
For edge-paring, I switched back from 6 edges at a time to 2-pair-method, but I don't think that's faster, it's about the same for me, use what feels better to you. I switched because I want to improve on 5x5 edge-paring at the same time, so it would be nonsense to use different systems on those two cubes.
Good luck, Robin