For those who have an aversion to power tools in woodworking, you'll want to avert your eyes for this. I have a Dremel tool jig for cutting the majority of the purfling channel. At the So. California Violinmakers Workshop last summer, I got to use a Fordham Rotary Tool set-up. Very nice. I'd like to get one, and may someday, but right now I have this. One thing I particularly liked was the foot-pedal power control. With the Dremel, the power control is on the machine -- really handy if you have three hands. But it occurred to me that I could build a kill-switch for the power to the Dremel to allow it to come to rest before I lifted it off the plate -- always a good time to really mess things up. So I went to the local hardware store and bought a big wall switch, a socket, a box, cover plate, and power cord.
Here's the box assembled, with the Dremel jig plugged in. In practice, the box will rest on the floor where I can operate the switch with my foot.
Here are the two plates with the purfling channel routed. Note that I stop short of the corners, and will finish that up by hand. Using the Dremel tool is still a stressful way to cut the channel, but it is clean and quick. It will take me longer to hand cut the eight corners and the button than it did to do this.
I should add that's it's always a good idea to plan these things out ahead of time. It's all in the design! :-)