the old man who taught me cabinetmaking taught me right. You can spend 3 times the amount of time trying to find a magical method or do it right . Assuming it is as bad as you say, I would think one would have to remove and replace the material under the vinyl. The time spent trying to find a quick fix could be spent taking care of it correctly.
Newsflash . Some people actually use a truck for work. Some actually buy a work truck . Now hold on to your chrome bumpers , some have regular cabs because they need an 8 foot bed and prefer the company of their dog ..... twopffenig