It's really simple. After you have the blades balanced, then you would rotate the prop, so that it turns more than one revolution. Put an index mark on one side of the hub, and if the prop always stops with the same side of the hub in the up position, then the opposite side of the hub is heavy. Use a drill and lightly remove a little material from the back of the prop hub on the heavy side. You will eventually make the prop stop at a random position every time.

Bill, Waco Brother #1