The top, rounded part of the Bauer slide is bead blasted. The slide flats are sanded smooth to about 320 grit. The frame is also around 320 grit. You can use wet/dry autobody sandpaper. Tape the paper to a clean, flat surface and rub the gun on it in the same direction as the existing sanding marks. 400 grit may work well, too.
Unless the magazine has burrs, there is no reason to sand it.