A couple of years ago we bought some Stockmar Beeswax Crayons, and they came with a little plastic tool for doing Sgraffito. Sgraffito comes from the Italian word sgraffiare (“to scratch”), and the technique works great with crayons. All you do is make a light color background, then color a dark layer (black is best) over the top. Then use something pointy (plastic works best, so you don’t rip the paper) and scrape the black to reveal the light colors below. We’ve been doing it for a year now, and it’s so cool. Almost turns out looking like a tiny wood block print.
I couldn’t find the tool that came with our crayons, so I just cut a point on this little green piece of plastic and scraped with it.