Barbecue paint is cheap and somewhat effective, but having gone that route before, bake on style ceramic or enamel finishes are probably better. You can buy a can of high temp engine enamel from just about anywhere, and after a sandblast and coook, it will be a lot more durable than barbecue paint.
That said, I personally wouldn't bother. My 500 security from the 70s has bed liner'd police style wood stocks, the bluing on the barrel and tube has turned into a brown patina (where it's still there), and the receiver finish is half worn off barbecue paint with scuffed up anodizing and silver bare aluminum on the high spots. It still shoots like a dream. Sometimes it's nice to have a gun you can bomb around in the bush with, throw behind your seat in the truck, drop, fall down onto, and let other people that don't care about your stuff as much as you do shoot.