Welcome to the forums.
I am not certain which vinyl you damaged on your dash, the hard or soft. The soft is difficult to repair and have it come out looking good. You might try polishing it with a mild abrasive polish which will dull the entire area. If it was the hard vinyl you can paint it. We did this on our dash using a product by Dupli-Color- Adhesion Promotor and then Krylon's Fusion paint. It comes in a wide range of colors. there is a paint for soft vinly but after seeing the results at a local body shop I was not satisfied. The soft vinyl can be replaced at a fairly low price, that is what we did.
Good luck to you. By the way what kind of motor home do you own?
1994 30' Excella 1000, Chummy III- Ford Excursion- 7.3 Turbo-diesel