For your exhaust manifold I would recommend the Manifold Dressing that Eastwood sells. It has the look of fresh cast iron, dark gray and a slight sheen. You just rub it on, I use a tooth brush. Each spring I like to go over it again, takes about 5 minutes, and it looks great the rest of the year. It comes in a small container and cost $20 but I've been using the same batch for over 6 years and barely made a dent in it.
