I love cooking with cast iron, but it can definitely be challenging at times to maintain the quality of my cast iron cookware. The easy solution is this: Caron & Doucet - Cast Iron Cleaning Soap. This product offers a cost-effective soap that will not damage your cast iron seasoning.
If there's a lot of rust you can use equal parts white vinegar and water, submerge the pan and let it soak and scrub with a mildly abrasive sponge. If you need to reseason your pan, place foil on your oven's bottom rack, oil your pan and place it upside down on the top rack and turn the oven on to 350.