milliput and Greenstuff mixed works a treat .. roll it out into a thin sheet and allow to cure for 10-15 minutes., cut and get the rough shpe right.. when it is dry sand it smooth and add in creases etc as detail on top of the cloak where needed.. (make sense).
the absolute best material IMHO is Magi Sculp but if you have trouble gettiug that a milliput / greenstuff combi will work fine...