I have a polymer (synthetic) stocked rifle that I'm contemplating some changes to. The rifle is a truck gun and I am satisfied with its performance as such. I don't want to replace the stock with Boyds or the like but the current stock is slippery and has a butt ugly checkering scheme. My idea is to fill the checkering and coat it with a truck bed liner coating. A project if you will.

What can I fill the checkering with that will adhere to a pre-scuffed polymer surface? Through research, I've ruled out JB Weld as I understand doesn't adhere that well to plastic. I'd be interested in a material that I could apply sandable skim coats to the stock without it popping off. Bondo? Marine-Tex?

Any advice would be greatly appreciated.