That hi-temp paint at local stores does flake off after about a month, no matter how good of a job you do. As far as Jet-hot goes, the sterling is OK on headers, but on PEMs you need the 2000+ coating, and sterling on the x-over is OK. Jet Hot takes about 5 days start to finish, you give them a CC# over the phone and your project description. They will give you a price and a job#. You send it down to them, they accept your parts with the assigned job#, and they complete it and send it back Fedex 2-day or less. I think it's about $200 for headers, but they coat inside and out. It really helps lower underhood temps. I have my PEM's and FWI coated form them, and the quality is excellent.
You can also get them powdercoated. You may want to checkout Pector on ClubGP, he's doing that now pretty reasonably.