I just use a pin vice. Army Painter’s, but there are a number of brands/options.
The one left of the files.
Holds up to a 3mm bit. I’ve got a two sets of bits, one “normal” one metric.
I’ve tried a dremal in the past, but they are overpowered for the job. You need precision more then power here. I’ve done some work as well with a large powerdrill. Unwieldy, but can turn slow with a light hand on the trigger. Prefer doing things by hand.
I hear Tamia makes a build-your-own powerdrill designed for hobby use. Light, small, and easy to use. On my list of things to pick up someday.