What is the best method to gain the most XP for a dragon that is level 80 in craft?

From 60 to 80 I was benefitting from making cobalt bars in Last Stand, and now at 80 mithril does not seem to give me as much XP for the time it takes and the work I do to gather it. Is there another way or should I continue making cobalt for now?

I would be grateful for any advice.