I've had good results with Brownells products.Haven't used the gukote yet but their aluma-hyde-ii
http://www.brownells.com/gunsmith-to....aspx?pid=1150
Stands up well to cleaning solvents and is tough as nails.
Trick is you have to put it on evenly ,with that get a bunch of spray nozzles(they clog quick) And bake it after spraying in oven at 350 for a couple of hours.