I got the marine grade flexable vinyl at Hancock Fabrics. Their selection is limited, but they carry it in more than one color.
You can try to pester me into doing it, but I've got pretty thick skin. I could probably be talked into doing another one, and I know I could do as well a job in a fraction of the time. -I probably threw the 'jig' away that I jerry-rigged, but since I used a scrap of drywall, it would not take long to make another. I'd probably spend more time trying to remember how I did it, than actually doing it. But if anyone wants pictures of my process, I still have them.
I never really understood the issue with the primer getting soft. I stripped off the whole mess, and started over with another paint. I assumed Eastwoods primer was better than what I had the first time. The second time around, I had no softening of primer, and no material pulling the primer off the dash.
I used no heat, but will see how that works out on the capping.