That powder has a normal cure temp and time - 450 degrees for 20 mins, so it shouldn't be tougher to use than any other powder. Like wbr has side prep is the key. Plus you need an oven that's big enough for your headers.
The only problem I see is that you want to coat used headers. That means they need to be blasted/cleaned then preheated to get any gunk out of the metal. No problem with the outside of the headers but how are you going to clean the inside? I guess you could rinse them and then keep heating them until there is no more smoking. Plus how are you going to coat the inside? If you don't coat the inside the headers will (eventually) rust from the inside out. The pro shops (and some hobbyists) have a wand that you can put inside the headers to coat the inside as well.
Home powder coating is great. It's just a slippery slope. The gun, the powders, the oven, the tape, the chemicals, a sandblaster - it really adds up, but you can get good results and if you plan to powder coat a lot of parts, it'll be worth it in the long run.
That's my .02...