Not sure what size the CB grates are, but here's an old oven cleaner trick. Spray the grates heavily with oven cleaner (the more caustic the better) and place them in a plastic garbage bag of some sort. Put them where they will be exposed to heat (in the sun is best) for several hours or even overnight. Then spray them off with hot water if possible. The remaining crud will be relatively easy to remove by scraping or scouring with a scotch-brite pad (wear rubber gloves). Anyway, works for my really cruddy grill grates.