Grab a friend.
Empty out your file cabinets (shred or throw out what you don't need). Less is more.
Take the cabinets outside and place them on a tarp or some bulletin board paper.
It will take about two or three cans per file cabinet. I always use the little gun, aka "spray grip." Buy one, they are only a couple bucks and they will really save your hands and nails;)
Allow the first coat to dry...then spray on a second coat.
Allow that coat to dry and then go grab your friends to help you move the cabinets back in.
Put them in a place where they will be a focal point. That was a lot of hard work and you should show it off for sure.