I have their cast iron grill grate. I use it on top of my cheapo wire grill racks. Grilling on cast iron is the best. I would still wipe your new grill grates with oil and heat in the oven to really give it a good seasoning. I've never had good luck relying on the factory seasoning of my cast iron. After that nothing to do but wire brush the grates after cooking and rub again with oil between cooks. Never wash with soap or any type of grill cleaners. Be sure to use a good quality stainless or brass brush or you will actually get rust from the minute particles of carbon steel from a cheap brush. A small amount of surface rust if it forms between cooks will wire brush right off.
Google their web site, the have much info there.