Use a few drops of lemon juice. Works every time for me. It'll last a day or several, then just do it again.
It's a natural bleach or fruit acid and lightly peels off the skin and reveals smoother skin underneath. You can moisturize after if you like. It doesn't dry out the skin. I leave it on for anywhere from 5 minutes and other times I forgot all about it until it began to sting my eyes and I just rinse it off.