Sanding cabinets before you are about to repaint is a smooth idea. Washing away the grime before painting your cabinets is a good start, but don't skip the sanding afterward. Sanding ensures new paint will stick and is also your chance to smooth away any dings or blemishes. Sanding also helps cabinets look new again, even before you apply paint. The more you sand, the better your final result will be.