It really according to the color of the stock. If it is brown, or similar, you can use a regular stock finish like oil, or poly. However, if it is some exotic color, like blue, you have to use a clear poly, or it will make the blue look green, if there is any yellow tint to the finish. Rust-Oleum has some spray on poly I've been having good success with. They also make a spray handle for the cans, and I would recommend that, as it helps applying it without runs, since its easier to control.
I sand all stocks down to a 600 grit before I finish them, and then use 0000 steel wool between coats. If you don't like a shiny coat, you can use this to bring the luster down too. Use a tack cloth, after sanding, and hang the stock with a wire, in a dust free place, before applying the finish.