Heard of that never tried it. But one I have used on a Mechanic that bragged he could diagnose any problem. Take a pencil and draw a line inside distributor cap from coil wire to ground very tuff to see without a flashlight
We did that to the Auto Shop teachers brand new 65 Mustang Convert. It was God's Gift to the World according to him. We got a class detention for that but it was worth it. lol