Hi,
i like your suggestion, but have you thought about this.
Copper tow cables and photo etch brass both do not like paint, it tends to scratch off easily and reveals the shiny copper underneath.
As with bright metal tracks (white metal), blueing solution blackens these. So there is a similar solution for blackening copper/brass.
If you blacken the tow cable or photo etch parts, you can then paint them. IF the paint chips, it will only reveal the darkened copper/brass.
Cheers from Australia.
Afrikakorps