Another suggestion requiring a bit more work is to cut out some circles from the stiff plastic used in alot of packaging (the kind that's booger to get open and will cut you if you manage to tear it and aren't careful), and then use a small hole punch to make a hole in the middle and cut a slit from the center to the edge of the circle. You can make different sizes quite easily both for different sized hackles as well as different hook diameters.
I also use these for separating deer hair colors to make stripes on bass bugs. Since I have multiple guards I can just leave one (or more, I've used 4 on one bass bug before) in place on the fly until I am all finished, then just bend it slightly at the slit and slide it off the hook.