I had never thought of doing this until reading a post on TMP. It was easy to put together and unlike Word or other programs, it's a breeze to move the units around (the little color markers you see on the map above).
The blue counters are American units (squares are BAR sections; triangles, flamethrowers; pentagons, bazookas). The red units are Japanese (various bunkers and rifle sections). The big orange shapes are rulers, for 8" or 4" (the two main measurements encountered in A Sergeant's War). I went for a very simple, quick map done up in Paint, just showing elevations and areas of brush. I superimposed the grid on the map as well; each square is 1" on the PP slide and 6" of "ground scale" in my game.