If you're at your wit's end with your regular sponge, look to steel wool to save your dish or cookware. Fine-grade steel wool can gently be used on cast iron, stainless steel, and enamel cookware.
Here's how to safely set steel wool (also called wire wool) alight using nothing more than a 9V battery. It's not difficult but you must take care as the wool and the dish can get very hot - adult ...
Steel wool is an invaluable tool in your kitchen cleaning ... but scrubbing that casserole dish after it's been baking for a while is the worst. Grab some aluminum foil, and make things easy.