Ceramic is highly resistant to scratching, that's the while reason for it. I was surprised when I first heard you could do this too, but sure enough the stuff is tough! It CAN scratch, but if you're not overly aggressive with it, just a steady off angle scraping (not 90° straight up), the excess paint comes off quite easily. There will usually be some stubborn drops of paint here and there, a soft rag slightly damp with alcohol will rub those off. Be careful not to rub in the triangle too soon, let it dry overnight first.
It takes a little practice close to the cutouts, especially the triangle on a non-pearl insert. You have to constantly watch that the blade doesn't nick the painted cutouts while scraping off the edges right up to the cut. It would be easier to use an exacto blade for this detail I guess, but I've done this enough to just be able to use your typical utility inch and a half rectangular straight razor blade.
The painting takes less than a minute. Dries almost immediately, then 2nd coat. Obviously do light thin coats and don't glob it in there. I waited about 30 minutes before starting to scrape. Scraping and rubbing takes about 30 minutes.
It's not a crisis if you mess it up first time around. Keep a wide mouth jar with some mineral spirits or goof off in it. A quick soak and light brushing with an old soft toothbrush, rinse in alcohol and you can try again. Wear latex gloves!