tried soaking in dryer sheets in bathtub, did not work too well.
I removed mine and scrubbed with SOS pad. It was hard work but it came off. Before I got to that point, I sprayed with a heavy duty cleaner for grills which helped to loosen the baked on mess I inherited.
I take mine out on the back porch and spray them with oven cleaner and leave them all night. Then I spray them off with the hose and there is very little cleaning needs done on them with Brillo pads. Hope this helps Phil