Here's the sequence of steps I used:
1 - Lightly rub the whole box with steel wool. Then brush off with a soft brush, then vacuum, then wipe completely with a clean rag with a bit of alcohol on it. [If there is any rust, you will have to sand a bit more aggressively before proceeding.]
2 - Spray with desired color of spray paint -- a very, very light coat -- not even getting close to covering the item color underneath. Keep the spray paint can away about 10" and move around quickly but smoothly. Never allow the spray paint to focus in one spot. Allow to dry. Sand with steel wool and clean again.
3 - Continue to add coats of spray paint -- a very light coat each time -- allowing to dry, sanding with steel wool, and cleaning each time. This might take up to 5 or 7 coats.
4 - The final coat should complete the color coverage. Allow to dry. After wards, with the finest of steel wool, lightly sand the project. Wipe with a clean cloth.
5 - When completely dry, tape off the handle part with frog tape. Slip a piece of card board in the file name slot place. Using a silver marker (or other metal color), paint the handle parts. Allow to dry, remove tape, and You're Done!