TLM, I've mentioned this long time ago in Wo Ai Wo Jia le.
Use it in combination of cleaning powder like Old Dutch (or the cheapest kind would do just as well), you can easily get rid of the old grease sitting on your cooktop.
I got mine from Costco. It's supposed to be only one-use product, but I recycle it :blowzy: Try not to squeeze it too much as it break into small pieces. It's actually the texture of the sponge that's most effective against grease. You don't even need to add anything, just soak it in water then start scrubbing. :glowface: