The way my grandmother did. Coat it with Crisco or any all vegetable solid shortening. Lard will smell funny. Turn it upside down on the oven rack and heat it to 350º for 4 or more hours. Let it cool in the oven. The excess shortening will drip off the skillet and not get sticky build up. Then she scoured the pan with hot water, no soap at all, then repeated the process. Her cast iron skillets were smooth as glass and nothing stuck to them. Not even an egg with no oil at all. She taught me to coat the spatula with oil before using so the food wouldn't stick to it.