I like to chalk only the paddle on a box and also on the push peg calls only the sound board. I use the brown chalk. No oils or wax to build up. As far as sanding goes I only sand the lips if they show sign of fraying or a shiny spot from fingers or whatever. When I sand the lips I make sure to use light pressure and sand the whole surface so I don't get a flat spot. Keep the same curve. The paddle gets an acroos the grain sanding so it bites into the sides,so to speak.