I searched high and low (in Orange County, CA) for someone selling round cooking grates. I have 12 levels that I could use but only 2 round grates (I believe 16")...Anybody know where to locate additional grates? The ones that came with my New Braunfels Smokehouse Smoker are shiny and black (porcelin???)...These have to be seasoned - Yes? Coat with oil and cook for how long (to season the grates and inside of smoker)?