It’s a general text, but "Centrifugal or Lost Wax Jewelry Casting"
by Murray Bovin has by far the best mold cutting advice. It has a
photo section of a variety of examples. Those Rio “Mold-Making for
Jewelry” videos were very helpful to me, also, though I had to watch
them several times as I kept falling asleep.
Mold making is as much an art as it is a skill. Practice is the
thing that will help you most.
Cut away from yourself! Cut away from yourself! Or wear a leather
apron and get one of those chain-mail gloves. Seriously. I sliced
myself twice in the beginning. Once in the thumb, once in the thigh
(I still don’t know how I slipped THAT far). A scalpel cuts skin and
muscle really, really well.