I can use both hands more or less equally these days, but it wasn't always so. I started just using my right hand, over time I began using left hand more and more. The left hand I believe has an advantage when using ATG pass on opposite side of the face. When i'm rushed I will revert to dominant hand shaving, and also pair that with a wedge type blade and get it done. When I have the time I tend to experiment with different grips and hand positions looking for a better way to get smooth. Everyone finds a routine that works for themselves I don't believe there is a wrong way to do it as long as the blade is doing its job comfortably.