It's very simple:
If the pot is on the smooth side and you find the pastels don’t adhere well, you’ll need to roughen it up first with fine sandpaper. It’s not usually necessary, though. Then colour the pot all over with the blue pastel crayon. Any surface irregularities add to the interest, as the picture shows. Now take your pointed object and scratch a design so that the background shows through. This technique is called sgraffito. We chose diagonal hatching which, combined with the surface texture, results in an abstract pattern. Then spray the pot with clear varnish. Two coats are better than one, but you should allow the first to dry before applying the second.
Be brave: experiment! Try different colours to suit your taste. Or create several different areas of colour next to one another: a tone-in-tone effect is very pleasing. You can use many different patterns for the sgraffito: wavy lines, circles, spirals, triangles – there are no restrictions on your imagination there.