Faster than using sharpmaker hone ( especially if it doesn't fit all the way through the hole), and "lower-tech" than dremel, you can take sandpaper like 200 grit silicon carbide paper and wrap it around a pencil to file inside of hole. Lower grit sandpaper will work faster than ceramic stone and can leave hole edge " toothy" but not "sharp". If too much "toothy" effect, you can use higher grit to smooth a little bit and, if too smooth, vice versa.
Regards,
Martin