Darth (Audio) Fader

A jealous audio man requested a Darth Fader for his audio board. Unfortunately, the controls are touch-sensitive, so I need to find some kind of a capacitive material to print this from - or paint it with - for it to work properly. For now I drilled a tiny hole through the index slot on top and ran a piece of solder through to make contact when you touch it on the top... (modeled for a fader with a 1mmx20mm slider)