Sometimes when I paint several color sketches or preliminary sketches before a larger painting, it can quench the desire to paint that subject. So switching up the medium can help me see that subject differently. Since I usually use oils, using pastels for color sketches is more direct and spontaneous than oils. The sticks of pastels keep me from getting too detailed. The pastel paper has a different feel than canvas. Then when I turn to the larger canvas, painting it in oils is still unexplored. So whatever medium you use, try using a different medium while you're working out the details for the finished piece and see if you enjoy the experience.