This is a fun project and my kids could do all the steps by themselves.
Colour with wax crayons all over a piece of paper (we did four papers)
Paint over the crayon with black paint, I used something random from a garage sale, but I think tempura or acrylic would work best. Allow to dry.
Use something to scrape your design into the paint, we used bamboo skewers, we did this part outside to avoid black paint flecks everywhere.