These are the steps I go through to prepare a tool or tackle box for planting.
1. Wash box.
2. Drill holes for drainage and screws.
3. Sand with medium grit sandpaper.
4. Wipe down with paint thinner.
5. Screw on metal strapping in pre-drilled holes to keep box open.
6. Spray first with metal primer, then enamel paint.
7. Plant it up!