At first, I thought this process was going to be more complicated or the results would look like a drunk 3rd grader's art project, but the sponge technique works great and is easy.
This is a Vertical Grip stock in straight Carbon from Stocky's that I used on a Win Model 70 .300WSM. The cheek riser I made from thicker knife sheath Kydex and secured with industrial strength Velcro; it never moves. I left the grip area unpainted, and so far, zero issues, very minimal scratches, even when pushing through lot of brush, etc.
I have my old Win 70 in .243 from when I was a teenager, and will likely do the same thing and let my son use it since the wood stock is pretty beat up.