Electronic – way to make your own conductive thread for wearable electronics

I'm not sure if conductive paint will tarnish - but I do know that the Graffiti Research Lab uses conductive spray paint to add tracks for LEDs around their work.

From what I've seen some of the work is on a regular exterior building walls. Even if there's no information on the website about your questions, I'd imagine they would probably know - maybe you should contact them if you don't have any luck by other means

Well, I had some fun with some conductive paint, which should be similar to your thing. First of all, check resistance of the 'wire' of it.

The main problem is reliability of lines. Also, it should not be able to physically hold elements in place, unlike solder.

Might be used to repair broken traces on PCB and especially, flexible PCB (cellphones, keyboards).