Hi,
I don't know that I'd bother ceramic coating (Jetcoat, etc.) a standard, cast exhaust manifold, if that's what you are working with.
IMHO, high temp paint works fine on cast manifolds and can much more easily be touched up at home, if ever necessary. Not to mention it's one heckuva a lot cheaper. Media blasting or certain liquid cleaners can be used to clean up the manifold and remove rust, in preparation for paint (or ceramic coatings).
By the way, Eastwood sells a product that just cleans the manifold and removes the rust, leaving a natural, original style bare metal finish. No paint or coatings, so it can be done with the manifold in place and also can be easily touched up every now and then. I've never used the stuff, but it's an interesting idea.
www.eastwoodco.com is their website.
On the other hand, I do think ceramic coating is practical and useful for mild steel tubular headers, if that's what's installed on your car.
/ubbthreads/images/graemlins/cheers.gif