My contribution at this nice modern art has been done in different ways, with a neon light, with a led stripe, and even with car's headlights ;-)
Now I explain you how to build a neon paintbrush.
Step 1: One option
Step 2: Another option
Here is the narrow neon tube already extracted from his plastic cover. This neon tube has both cables come out from one extremity, but if you look closely you see a very thin metal wire which runs side by side the tube.