Ultracortex3 - Sanding Mechanical Parts
The tutorial suggesting sanding the electrode and spring holders after the wires were attached.

That seemed a bit cumbersome, so I decided to sand them before adding the wires.
II made a tool to hold the spring holders with a piece of chopstick and electrical tape.
I inserted that into a drill and held my sanding block and sandpaper against the pieces while the drill was on.
The electrode holders were done by inserting them into to drill with two nuts on the screw.
Cleaned up dust by holding a towel to the piece while spinning.