Ive painted a lot of things, but I dont paint handguns. Never thought it would hold up well enough to bother, even with the more expensive/permanent type paints. Between going in and out of holsters, and getting banged around, I really dont see it holding up well for very long.
Krylon works OK in general, and is removable, which I prefer, in case I change my mind down the road. Ive used it (in part) on a number of guns in the past, and it does OK.
Krylon does have their "Fusion" brand, which is supposed to bond to plastics, and be more durable in that respect, but I havent used it, just for that reason.
I have used Brownells Aluma Hyde II on a number of things, and it works quite well. You do have to follow the directions exactly though, or you can and will have troubles. It is more permanent, and may be a better choice for something like a handgun. Duracoat, and some of the others might even be better, I just dont have any experience with them to say. Downside to those type of things is, if you dont like the finished product, youre likely going to need a bead blast and refinish to change it.