Yeah, I get what you're saying and won't dispute it. I didn't say it was ideal, or easy, or that the results would be perfect, or be at the level of a 'professional' - only that headers could be coated with a product such as the one I named. My bad. I had access to the right prep tools, a large PC oven, (no vibratory tumbler but paper, buff wheels and compounds) and, under the circumstances, got the results I expected. Although they have dulled some with heat, there's been no pits, peeling, or rust since 2012 - and that was after removing an old coating. They still look good/decent - better than paint.
I was under the impression the OP was interested in options. I presented one - without any warranty.