From about my 2nd or 3rd shave I committed to learning to use both hands. Oddly enough, my off-hand (left) shaves better! I think it's because it felt so unnatural, i was more attentive to correct angle, grip, light touch, etc. By watching my left hand I also learned to pay more attention to my right hand as well.
I'm very glad i use both hands also because, as some have noted, it makes it easier to get good lines of sight on some points of the face.
I'd suggest taking it slow. Just use your left hand to shave the sideburn on the left side. Then take it down more, then the whole check, the neck, etc. I now use both oblique strokes and the circling motion as well with the left hand. I still pay extra attention when the razor is in my off-hand, but again, shaving with straights is all about paying attention!