Inside, boil some dishwasher detergent or baking soda
Outside, scrub with steel wool and barkeeper's friend
David....Bar Keepers Friend works well...Walmart and most grocery stores.
Hi David - This is a great tutorial on how to clean, season, and care for cast iron skillets. Hope it helps! Hugs, Holly
PS - We have a FREE eBook with recipes for all of my homemade and all-natural cleaners. You can download it here --> https://pinkfortitude.com/thank#GreenClean