This is not exactly what you asked for, but it's probably worth mentioning that a good way to do manual machining once you have converted a manual mill to CNC is to do it electronically via the steppers, using a hand-held controller. sometimes called a "pendant" or "MPG" (manual pulse generator).
While you could use dual-shaft stepper motors with handles connected to the aft ends of the shafts (and some people do that), that can lead to problems with the steppers acting as electrical generators which will back-feed voltages into your stepper driver electronics if they remain connected while you are cranking them and which may possibly result in the release of unwanted "smoke" as well as much in the way of loud and colorful cursing.
BTW, the last mention that I can find of the Southern NH CNC Club is from over a year ago. Does it still have meetings? Is there a website for it? I have moved out of Southern NH (I was actually living in SW NH, in the Keene area), but I would like to return there someday if things work out well.