Lay out five or six sheets of newspaper on the ground for each grate you want to clean. There should be a minimum of 6 inches around the sides of the grate for over spray. Make sure that you place it in an area where no children or pets can accidentally step or touch it.
Place the grates on the newspaper, centering each of them on their pile. Spray them with the oven cleaner so that they are totally covered in the foam. Put on your rubber gloves and turn the grates over so that the bottom is exposed. Spray it with the oven cleaner in the same way, making sure that you don't spray into the wind.
Let the grates sit for about 20 minutes or whatever the instructions on the container specify. This will allow the cleaner to dissolve the residue on the grates without any scrubbing or scratching of your ceramic grates.
Wipe the cleaner off with the paper towels, making sure not to get any of the spray on your skin as it will burn quickly. After you get as much of it off as you can, flip the grate and do the same to the other side. Put the soiled paper towels into the plastic trash bag so that no one else touches them.
Roll up the newspapers and put them in the plastic trash bag as well. Rinse the grates off with water from a garden hose to remove any of the oven cleaner residue.
Place the grates back on the grill and turn the grill back on using the normal safety precautions. Close the cover and allow the grate to heat up and burn off any chemical smells from the oven cleaner.
Open the grill cover and apply a thin layer of vegetable oil with a rolled up soft rag. Rub it quickly so that you don't burn yourself. Turn the heat off and allow the grill to cool down. Your ceramic grill is now ready for use.