Hang the skin 1/4” over the table edge. Weigh the skin down with heavy weights or use a clamping board to keep it from moving.
Here’s my technique. You are looking over my left shoulder. Run the belt generally with the edge of the skin, but with a slight angle to keep from grooving the belt. Apply pressure slowly when beginning or ending a stroke. Keep it moving! Think like you are working with a paint gun. Lift the leading edge of the belt slightly when making a stoke to keep from digging in.
The skin will start to wrinkle on the edge as heat builds up. Take a break for half a minute to rest and the skin will lay back down as it cools.
Final smoothing of the edges with some 600 or finer AO paper on a foam block was easy following this method.