I've got one of those pens, just haven't gotten around to trying it on anything.
Here's the one I got:
https://www.amazon.com/Molotow-ONE4A...WG7T5S3R3RP2E5
Here's another vendor:
https://alsacorp.com/
And a video of what appears to be magic:
https://www.youtube.com/watch?v=GY0iNcApC8s
I was going to try this stuff on the dash corner vents. 70's were one year only on the vents. Impossible to find NOS.