From the GC&W layout thread:
Mike, CHEAP CONDUCTIVE GLUE! 
What a brilliant idea! Why didn’t I think of that? Please share more detail...perhaps a dedicated thread?
Thanks, Otto
Don’t they already make conductive paint?
Yes, there is conductive paint. Have you ever priced it? Yowee! (It usually contains powdered silver.)
I've been fooling around with various tricks for DIY conductive paint or glue with the intent of building resistor wheelsets for signal detection. I use FVM resistor sets by the barrel, but with good-looking wheels now coming standard on higher-end rolling stock, it seemed such a waste to throw all those wheels away just because they don't match the one FVM resistor axle I put on each car.
The DIY paints I've seen on YouTube, graphite powder blended into acrylic paint, never seemed to work for me. Then last night it dawned on me, "What about CA?" Yep, it worked. It worked
really well.
It's simple - squeeze out a 1/4" to 3/8" dot of regular CA onto something impermeable and disposable; I happen to use PostIt note sheets. Completely cover with hardware store graphite powder, the lock lubricant stuff. Stir - I use a toothpick - and keep stirring until you've worked as much graphite into the glue dot as it wants to take. Done, you now have a paste of conductive CA. The graphite extends the CA setting time, so you might have 10-15 minutes of usable open time for whatever project you're working on.
Now this is not "zero ohms", and can't be considered a true conductive paint. The paste when "painted" in a line will make a resistor. In this example, the line is about 1/16" wide, and as you can see results in very roughly 6K ohms per inch:
First try at sticking a resistor to a wheelset seems to be working, but a little bit of sloppiness with the paste compromised the resistance to 7K instead of the 10K of the resistor. But it'll work.
Something to be aware of is the resistance doesn't settle to its final value until it is dry. I was getting 100K per inch when the 1/16" test line was still a little wet, a far cry from the dry value of 5-6K.
