I use a bicarb and water paste, spread it all over and wait five minutes. Then scrub off with a scourer. If there's any rsidue, I use a rag soaked in vinegar and wipe over the top of it with that.

I did heat and steam it first, but I don't honestly know if it makes a difference.

Oh, and for the racks, I put them in the laundry sink with bicarb and hot water, then soak and scour when they're cool. appletree's aunty has a nifty trick for cleaning racks, but I can't remember it.