Quoting from an article by Dean Torges on how to restore an iron skillet that sticks:
"If the skillet has cooking oil on it, wash it with warm soapy water. Never again rub it with oil; never again subject it to soapy water. Dry the skillet and rub a thin film of Crisco vegetable shortening, or tallow, or lard (such as bacon grease or rendered bear fat) over the bottom with a crumpled section of waxed paper or paper towel. Turn the burner to medium heat. Within 10 minutes, the film of grease will dry up and coat the bottom. After it dries, repeat the process. Do it several more times; lay in a thin coat of grease in the hot skillet bottom, wait til it hardens, then lay in another. It will smoke slightly upon application, but soon you will have created a slick, moisture resistant, hardened film of grease."
Dean is a consummate iron-ware chef; check out his web site at
http://www.bowyersedge.com/ for some mouth-watering examples.