cleaning a cast iron skillet

My mother recently passed away. I found a very unique cast iron skillet I would like to use. It has some rust on it. I put it in my self cleaning oven last night while I was cleaning the oven. When it came out most of the rust had peeled up in sheets but there was still some remaining. It is a cornbread pan with segmented portions. Does anyone know how to remove the rust in a safe manner so I can begin using this pan? I would appreciate any suggestions.
Thanks!
Janet