I've done a few. With some history painting other polymer stocks, I use the Krylon Fusion, when possible, as it seems to adhere better than most, as some others have mentioned earlier.
My takes on some of the Altus/Manners color schemes on a couple of KRG Bravo stocks and a Boyd's PV. Stock base colors with torn pieces of Walmart bath sponges torn into random chunks and dipped into puddles of sprayed Krylon. Light color first, followed by darker color. No clear coat needed, to date. Obviously, colors can be varied and additional colors could be included. Less is more when sponge painting, imho.