Pigment Sticks are very soft and have very little wax in them compared to other oil sticks. But the wax that is there and can be used in this interesting technique. By lightly fusing the paint with a hot air gun you can get different effects.
You can get melting and running effects. Some Pigments may sink below other layers and some colors may rise up.
But the greatest advantage is speed. Fusing does not dry the paint, but it does make it somewhat tacky. So it dries it enough that you can pass another color lightly over the surface and leave another layer behind. This way you do not have to wait days between layers. This painting was done in one session.