Ey Dax, that does look cool! The skirt that the arcs wear is called a kama and I have made em with paper mâché using tissue paper and white glue using a plastic potf vader Kama as a mold and building the Kama on the inside of the mold. It is easy and works pretty slick.
I belive I have documented this early in the first 20 pages of my custom figure thread somewhere but can't remember where. You would just have to look for it.
I will have to do a tutorial for this and a full cape using the same material, sometime in the future.