To get the majority off, I use to (when I had a ceramic top) wet a paper towel with ammonia. Let it lie on top of the burnt area along with a piece of saran wrap over it to prevent drying. I usually left it on over night. Less elbow grease, less work. This also works in the oven. For the racks, put them in a garbage bag along with a cup of ammonia and let sit over night. Wipe off in morning. When I was in the Navy this was the easiest and cheapest way to clean.