I finally got my act together today and spray painted all my letterboxing containers at the same time. For those of you who don't go letterboxing and have no idea what the heck I'm talking about, letterboxing is a hobby where boxes containing a hand-carved rubber stamp and logbook are hidden along trails for people to find. It's common to try and camouflage letterboxes with camo tape or spray paint. Lock n' Locks are by far the best plastic containers available, holding their water-tight seal even after repeated rounds of freezing and thawing.
Black is the color of choice for spray paint since boxes are hidden in dark holes. This was about 25 boxes and it took me five minutes to spray paint them once everything was laid out on the paper.
I use a very light coat, since you need just enough to conceal the container (not actually give it a good coating) and a light coat is less likely to chip off. I leave the stickers on while painting and remove them after the paint is dry to create a clear window into the box (in case some park police think it might be a bomb or something).
OK, now I've got lots of boxes all set to go. Time to make some stamps and logbooks!