Occasionally, you may notice the cooking grate is not getting cleaned no matter how much scrubbing/scraping/brushing is done and that it needs that "extra touch" to get it really clean. Smoky calls it "Purification by Fire". To get your grill "purified", light a generous amount of charcoal and place all over the charcoal grate, maybe even more so around the edges where the built up grease is situated. If you have a generous amount of buildup on the cooking grates and if the fire is hot enough (and it needs to be), the buildup of old cooking greases will catch fire and incinerate. When the fire dies down, it is then easy to brush down and have a clean grate.
This method also works great for grills where you do a lot of indirect grilling (i.e. heat on one side and meat on the other). Meat juices will collect on the one side and then flare up occasionally when they come in contact with the fire. It is best to do this in a controlled setting before beginning to cook. You do not want to cook new foods in the flames/smoke of old burning grease! When you are finished with the purification, it's time to start cooking!