marajo, try scrubbing with really hot water, the steel wool and NO Joy. CI retains bits of stuff and sometimes you will get a "soapy" taste if you use a detergent. If you can get it off without soap that would be best.
You're only given a little spark of madness. You mustn't lose it. Robin Williams Alix
Best to use oven cleaner, put in a plastic garbage bag for a couple of hours rinse and wash. I use solid shortening instead of oil will not leave residue. Work in the shortening with paper towel, wipe off all remaining till shiney. Will work best if you have a gas grill. Turn all burners on, invert bake for an hour and shut off to cool.