Got a cheap metal wallet. Decided to give it a paint job for kicks. It'll probably chip over time, but the last time I used a sealant on a project the paint smeared everywhere so I'm hesitant.
Besides the usual, I carry some basic first aid in there.
I'd use a spray lacquer but only after the paint has been drying for 48 hours. You should do very very light coats many times. Too much and you'll probably ruin the paint job. The lacquer layering will also take a while as you have to let it dry before applying more.