When I first started straight razor shaving I pretty much used my dominant hand for the whole shave. I knew damn well that I should have been training my left hand to shave but I was lacking patience and wanted to see how well I could get a decent shave done. Eventually after the fear factor of the blade subsided and I got some confidence then I focused on left handed shaving. I do see the advantages of ambidexterity in str8 shaving there are going to be spots on your face that are just easier to get using one hand or the other. Certainly you will be able to see what you are doing better by using both hands. Even after saying this I still don't see anything wrong with using the hand you are more comfortable with to shave, after all the goal here is to actually finish shaving and enjoy the result. I think that its just a choice. I believe many ways to skin a cat. Explore them all see what sticks and whats enjoyable and make it yours.