After the grates and panels have soaked, take them out and scrub them thoroughly. A long handled grill brush offers added leverage. For really stubborn gunk, a paste of vinegar and baking soda helps the brush scrub off the worst bits. Rinse them clean. Take care to thoroughly dry cast-iron grates. Now’s a great time to inspect porcelain grates for chips that may lead to rust later on.
Clean the bottom of the grill with a soapy sponge. Once all the chunks are gone, scrub the bottom with a sponge or scouring pad and soapy water to remove any built up grease or grime. Lots of drippings and food scraps tend to build up under the burners of the grill. Pay close attention to this area and clean it as much as possible to avoid corrosion.