Lots of possibilities here! Thanks, all.
It may come down to what I can pick up locally at the supermarket, auto parts store, or hardware store. I may have time to drop in on the first two after work and scout around.
I do have an automotive plastic/vinyl restorer on hand. It's a liquid, not a paste, and doesn't quite sound like any of the the products being mentioned.
A dullcoate approach did come to mind but I haven't been happy with the Krylon version. I used it on my layout "scenery" to reduce glare -- basically photos in plastic display stands -- and it "glopped" in spots and was impossible to fix. Also, I don't yet know how this truck will be used. The other one will definitely need to keep its high sheen for an auto restoration scene.
TRRR
