1. When casting is dry, varnish both sides of the casting to seal it before painting (so wet paint won't make design disappear) and for more sturdiness. Let dry. Optional: Apply a 2nd coat of varnish for more permanence.
2. Apply paint to boot design, one color at a time, letting paint dry between coats so paints won't run together.
3. Optional: Apply another coat of varnish to protect painted casting.
4. Optional: Glue magnet to back of casting.