This is one way to paint hive boxes (or supers). Hang them between two saw horses (like Rusty does at Honey Bee Suite) and paint them:
I don’t have any saw horses, but I managed to improvise something like this:
Here’s the video:
I painted my hives with linseed oil when I first got into beekeeping because I was all hung up on being as natural as I could be. I still like the look of the natural wood, but the linseed oil doesn’t last. I’d have to repaint the hives just about every year if I stuck with linseed oil. I use 100% acrylic latex paint now. The colour isn’t so important, but I picked a dark green so it’ll heat up in the sun on cold days. We get plenty of those in Newfoundland.
A drop or two of paint inside isn’t the end of the world, but paint on the bottom or top edges is not a good idea because it acts like glue and creates some pain in the neck difficulties when removing supers or inner covers, kind of like trying to open an old window that’s been painted shut.