How To Scull
The picture below is this "slicing" back and forth with the oar causing the boat to quiver in the water.
Later, I tryed experimenting by slightly turning the oar at the end of the stroke until I felt resistance as the oar tended to dive into the water. This is when I first noticed the boat starting going forward. From there on, things started to get easier every time I went out.
Even though the sketches below are of a "knotch in transome" type instead of a "through the transome" type - the theory is the same.
Sketches by permission of S.F. Manning - Camden, Maine. For more illustrations as well as text regarding "how to scull," go to the links section of this website and click on the link "How To Scull : Illustrations and Text by S.F. Manning."
The picture below is of a young sculler at the helm showing the distance of travel at the end of the oar from inside the cockpit - which turns out to be 11" off center in each direction from a 32" wide cockpit.

Photo courtesy of Greg Stender
Additionally, I found a "scull hunting video" for sale at Lock Stock & Barrell which is an excellent video on this topic. It is a 2 hour long video of scull hunting, set-ups and sculling instructions. It shows scull hunts on Goldeneye, Bufflehead, Mallards, Woodies, Bluebills, Merganser, Redheads and Coot. and sells for $25 + shipping and I would highly recommend it for anyone trying to learn to scull.