I remember when I first saw Bill Young's material drawing demos.
My reaction? "YOU HAVE GOT TO BE KIDDING ME!"
I thought for a few seconds about trying to draw with materials myself.
Materials have scared me ever since.*

*Kidding I thnk. Bill and the other material masters sure make it look easy compared to my attempts which have never gotten far. Maybe some day I'll 'get' materials. The Anzovin CDs definitely opened my eyes to the possibilities.