I have used a copper-based paint that has a resistivity close to that of a metal. It brushed on like thickened latex house paint.

My application was to create a dielectric roll for corona treatment. The roll itself was wound using filament wetted with a high-dielectric epoxy. The inside of the roll was coated with this copper paint. I remembered measuring less than 2-3 ohms across a 100" long roll.

This paint was also advertised for forming continuous, six sided EMI/RFI shield inside a plastic box. Unfortunately, you would have to buy 5 gallons or so at a time, and it was not cheap.