Heat the cast-iron pan on the stove until it's warm, but not too hot to handle. Scrub out as much food residue as possible with a scouring pad and hot water. Chip away at difficult-to-remove residue with a dull knife or chisel.
Place the cast-iron pan inside a self-cleaning oven, and activate the self-cleaning cycle. This will serve to burn off any remaining residue and reduce it to ash. Allow the cast-iron pan plenty of time to cool before removing it from the oven.
Clean out the ash from the cast-iron pan with hot water and soap. Remove any remaining rust by scrubbing out the pan with steel wool. Start with a rough grit of steel wool and work your way to a fine grit.
Clean any residue from the cleaning out of your cast-iron pan with hot water.
Season your cast-iron pan by coating the inside with bacon grease, lard, or another type of cooking fat. Use a towel to evenly distribute the fat, then place the pan inside an oven heated to 250 degrees Fahrenheit for 15 minutes. Remove the pan and pour out any extra pooled grease, then bake the pan for another two hours.