I've tried this a little with a couple cards I had here. There seems something of a trick to it. I've had better luck getting a show-ish finish sanding off the gold down to the copper base before hitting it with paint, but it's easy to go too far and take off the detail as well.
Same thing with the paint really. Too much and all the paint comes off and you might as well have not painted 'em. But there's a "just right" part where enough paint remains in the hollows to make the designs stand out.
Anyhow.. it's trickier than it sounds (at least for butterfingers me. ) .. so if anyone's making a deck, it'd be worth it to get an extra card or two to practice on.