I'm not sure if that would help or not. You have to coat the inside too. Try some enamel or lacquer paint on a scrap of the vinyl.
If you aren't in a hurry to build the kit, take a piece of parts tree an do a test. Paint some, clear coat some, and leave some bare, and leave them in contact with the vinyl for a few weeks.
Those parts are so stiff, it makes posing the models difficult. My Griffon's legs were always spread, so I couldn't make any dramatic poses. :(