Is it against the rules to use multiple drills, but not at the same time? I would like to set up 10 drills each with a pencil in it in order to save time that would otherwise be spent changing the pencils between sharpenings.

It is against the rules to use multiple drills. The rules specify "an electric drill" Also the pencils must not be in the drill at the start of the attempt. This has always been the intention, however, it was not in the rules before, so i just clarified that.