I have never poked a hole through a vinyl padded dash, but I have had to cut nice looking reliefs, pockets and thru holes in medium and high density EPS (expanded polystyrene) up to 3" thick. We were shipping motorcycle transmission gearsets, clutches, etc. heavier type stuff. We used a Hot Foam Knife similiar to this one:
https://www.amazon.com/dp/B06XWF64VZ...a-367031114586
It wasn't super fast, but it was precise and could work good for your dash for removing the dash pad to access the steel. It seals the cut edges as well. We bought ours from Hobby Lobby locally, but I would imagine that a Michael's Craft Supply or similar place might carry one. Good luck