I just started shaving with a straight razor ten days ago and used both my left as well as my dominant right hand, from day one. I figured that since the feel, coordination and skills required to using a straight was altogether different from shaving as I had, with a double edge, it might be better to develop the muscle memory and coordination shaving with right and the left hand, from the start. I shaved my entire face from the first day, with few mishaps. I went very very slowly. I'm still very slow.

Michael-