The other day I went to our local YMCA shop & found just the thing I was looking for - a cheap, boring, bog-standard shelf unit to use as display at my next fair. Of course I wasn't to let it get away without being painted within an inch of its life... and of course, I haven't bothered with a before photo, but I'm sure "crappy flat pack pine unit" isn't too hard an image to conjure up.
I thought I'd experiment a bit as it's not for selling. I wanted to achieve a "chippy" paint look, like its been knocking about for years (insert your own joke). So it got two thick coats of Annie Sloan Chalk Paint, first in "Florence" (dark green) and then "Provence" (French-style greeny-blue). After a layer of clear wax, I attacked the top layer of paint with a screwdriver. After that, there isn't much of a method, but I played around with dark wax, watered down white paint and generally building the layers up until I was happy-ish with the look. It was all sanded smooth, finished with a good layer of clear wax and finally buffed to add a smooth sheen.
I prefer this worn out look to just sanding the corners a bit, but I think it's worked better on the edges than anywhere else, but it will be fine for display.