My blue flared car has fiberglass flares. They're all glassed in, filled and painted on the outside... But on the underside, it's just a bare cut fender edge and rivets. The metal wasn't worked to fully butt up to the fiberglass, so there's gaps that need to be filled. I don't want to pound on it as I don't want to crack the fiberglass.
Is there a good product for sealing this up so it doesn't rust? The car has not been driven since the flares were installed, so it's still relatively clean under there.