As already mentioned, alum on the fingertips does wonders for me in being able to keep the skin pulled tight. When I transitioned to a shavette from a safety razor, almost all of my nicks/cuts were attributed to the motion and not the angle. The safety razor allowed me to develop a bad habit of adjusting direction mid stroke, this swooping motion would induce a cut almost every time with my shavette. I learned the hard way to only move the razor in a direction 90° to the cutting edge and to make sure that my wrist stays firmly "locked" during the pass.