Anything that can pull apart the molecular bond that makes paint, is likely going to do the same thing with a synthetic stock. So soaking it all the way off can cause some problems. Some high grit sand paper should smooth out the textured part, then some flat black spray paint to give you a starting point would probably work well. If you want to try the chemical route I'd soak a rag and basically scrub the surface, basically sand it with paint thinner.