I'm really not familiar with the whole HOK line but they should have a plastic primer or some kind of adhesion promoter to use.Certain plastics will hold sealer and paint fine but the newer mirrors aren't that great.You don't even have to scuff them with the primer,just clean them real good and go for it.That way you keep the original texture without any scuffing scratches or flattening the texture (if there is any,haven't seen a newer GM in a while).Someone else will jump in with product info for you.
