This is my drill press with a dowel rod inserted into the bit holder. The dowel rod fits perfectly inside the 1/2" button back. You do not have to turn the drill press on, just position your button under the dowel rod and pull down on the handle. This set up would work for larger buttons also, just attach a larger dowel rod to the smaller one, or a piece of wood cut to match the back of the button you want to cover. I plan on using this set up mainly for the smaller 1/2" buttons, the larger buttons I don't make large quantities of, but if that changes I now have a set up I can use.
Here are 2 samples of my button bracelets.
I hope you find this useful!