3. To help prevent fish from sticking, make sure your grate is clean and well oiled. After scrubbing the grate with a wire brush to remove any burned-on food and ash, get your coals glowing red. Close the lid for about five minutes to super-heat the grate, then dip a paper towel in canola oil and, using tongs, wipe the grate down generously. Close the lid again and let it heat up for a minute before adding the fish.