I don't see the allure of painting a gun with spray paint. If you want the gun camo'd why not do it right and at least have the pretinant parts dipped with a long lasting finish that won't flake off in the action and inner workings? Why anyon would take a $1000.00 or so gun and subject it to krylon or a HD special treatment is beyond me.
As to making it harder to see for hunting, I've hunted ground blinds, tree stands and stalked with wood stocked rifles all my life and never had an issue with the gun giving me away. If it did, I'd be more inclined to believe it was from solvent residue or just my movement over anything.
Its your gun, you do what you want to with it but personally I wouldn't devalue or risk the workings on it with a cheap can of spray paint.