I havent personally but some friends of mine have. Recommendations of you can take the case fully apart do so (but remember how to put it back lol) , will make to process a lot easier, make sure he know what he is doing, also make sure the paint can withstand higher temperatures because things will get toasty inside there and you dont want paint flaking on in a few month, i also suggest using a high temp clear coat as well just to give it that extra layer of protection, good luck

I would only paint the outside of the panels/doors.

Also adding onto what Z06 said, make sure you do even, but as few coats as possible. "A room gets smaller every time you paint it." Is it minuscule, yes, but the standoffs for your motherboard are the main concern, because if you put too much of a coat on them, where it doesn't fit like it should; now you're forced to put pressure on the motherboard to "force" it down, which peels the paint, possible gets stuck to the motherboard and in the worse case scenario, you run the risk of snapping a piece or more off your motherboard depending on what pressure you're forcing. And as he said about choosing quality paint that can handle extreme heat, that is also true. There are pure shit paints out there, that can - keyword CAN - become wet from excessive heat and you absolutely don't want that in your system (Acrylic paint would be my best bet for paint that can get wet from heat, but I can't imagine you using that.) Other than that, if you get paint that isn't suitable for heat, you're looking at burnt paint, flaking paint and the worst in my opinion, peeling paint. Peeling I say is worse because that could be a whole strip that falls off, the fans either catch it wraps around the bearing on the fan or gets blown into your GPU and there's that whole mess. Those are freak scenarios, but very possible.

I have done this twice now... It never turns out how you want it to lol.

Only do it if you're sure, but if you can make a one of a kind case, go for it. They can look amazing if done correctly.

I would just pay the premium for a hydro-dip. Usually isn't too expensive depending on the design.