when teaching technique, flash is the last thing to worry about. If you want to learn to manipulate light, you need to learn how to see it and then make it do what you want w/o adding any more than whats there to begin with.
I can light a model with one light source and produce a main/fill/back/highlight.
One of the biggest things I preach is that a camera and equipment is nothing more to a photographer than a brush is to a painter. It's a tool.
A brush cant make you a painter.