I use Easy off oven cleaner, let it soak, rinse and repeat if necessary. At that point, most crud comes off with the sos. The oven cleaner is caustic, so use caution and wear gloves and eye protection. Don't breath it!!
Just out of curiosity... Are any of you guys polishing with a dry 0000 piece of steel wool after its clean? Using any kid of liquid or comppund with them?
I've cleaned many grills with Dawn and a sos pad, but never polished anything dry.