A lot of the new cast iron out today is pre-seasoned. The oven method will work but the best way to season out cast iron is to cook in it. cook up a pound of bacon or deep fry some potatos. I don't recomend washing casting iron except under extreme circumstances, just scrape it down good with a metal spatula and wipe it clean. If you do have to wash it don't use anything like brillo pad just a rag and lite soap then wipe it down with oil before you put it up.