I line the hutch with newspaper (not suitable if the buns chew it) and then stuff it with hay.
I dont use anything else - some people line litter trays with megazorb - i again, use only newspaper and hay - it needs changing daily and probably twice a day in the summer.
Sawdust is def not recommended. Some people use straw (so long as they still have regular access to hay).
Hope that helps?