Scrubbing the stummel in hot water with Murphy's oil soap will many times remove stain. Use a toothbrush that has stiffer bristles. The stain may not be totally removed, but for the most part it will be gone. Briar doesn't have the problem with grain raising when wetted.
Sanding should be used when you need to repair blemishes, like when steaming out dents. In my opinion sanding to remove stain is a little too aggressive. Add since micromesh pads usually start at 1500 and go up, you'd be doing a lot of sanding. If I was to remove stain, I'd probably start at 320, and use flexible sandpaper.
Sanding has it's place, but if you don't have a lot of experience you can devalue your pipe in no time flat. I've seen furniture, gunstocks, and pipes that were sanded into oblivion.