I'll second the Aluma Hyde II. I have used it successfully on trigger guards and other small parts, and am thinking about using it on a stainless barrel that had the Cerakote where off.
I have used the Krylon on stocks and one barrel. To me its just too crude for metal work. One tip for using it: if you use it on a stock, make sure to put a clear matte finish over it afterward. This greatly increases the lifespan and reduces the need for touch-ups.
