I've had some luck with 3M body schutz used as a rough coat. It is sprayed on and leaves a rough texture that is paintable in 24hours. It is extremely tough to chip or remove. Herculiner makes a kit for do it yourselfers, polyurea the truck bedliner material can be painted after allowing dry time and scuffing up with a scotchbrite. Most chip guard stuff will gouge easy if you slide heavy objects on it. I'm interested in some other ideas, because this has come up over the years and I have tried all of the above. They all worked, but They all left me looking for something else.