We enjoy cooking with cast iron skillets. They are interesting to clean. While watching Food Mob! there was an email question someone had about cleaning and using cast iron. I asked my mother-in-law for her steps in proper cleaning and maintaining cast iron. Enjoy!
If it has any rust It must be completely cleaned of rust. I did this by putting it upside down with the lid on top, on the rack of my self cleanning oven and setting it to clean for two hours. Allow the oven to completely cool before removing it. after removing it from the oven you need to scour it with steel wool under hot running water without any detergent until all surfaces are completely clean.
To season your skillet I recommend using an outdoor gas barbecue in a well ventilated area. Using the kitchen oven will smoke up your house. Preheat your barbecue or kitchen oven to 375°. After your skillet is dry, place it on the barbeque or center rack of your kitchen oven with the lid ajar. Allow it to warm slowly so it is just barely too hot to handle with bare hands. This preheating does two things, it drives any remaining moisture out of the metal and opens the pores of the metal.
Now, using a paper towel or a clean 100% cotton rag, apply a thin layer of vegetable oil. Make sure the oil covers every inch of the skillet, inside and out and replace it on the barbeque or oven rack, this time upside down with the lid resting on top . This will keep oil from pooling in the bottom of the skillet. Bake the oven for about an hour or so at 375°. This baking hardens the oil into a protective coating over the metal.
After baking, allow the skillet to cool slowly. When it is cool enough to handle, apply another thin coating of oil. Repeat the baking and cooling process. When the skillet can be handled again apply another thin coating of oil. Do not leave any standing oil in the skillet! Standing oil can turn rancid ruining the protective coating you just applied. Allow the skillet to cool completely. Now it should have three layers of oil, two baked on and one applied when it was warm. The skillet is now ready for use. You can do this same procedure with dutch ovens.
I never wash my cast iron with detergent. You have to be careful the first few times you use the skillet, because cooking with sugar or tomatoe based food can remove the seasoning. I use it at least three times applying a thin layer of oil after washing in hot water only, before cooking with tomatoe or sugar. I hope this helps.