Keep them in the dark, that's supposed to increase the potency. As far as mold goes, pedro cuttings can last months without rot or any such problems. You have to worry about new growth before anything else. I had a foot-long cutting in my closet for over a month and it started to sprout little buds off the side.
By open flesh, do you mean the fresh part at the bottom of the cutting? A little bit of air-drying should keep it from rotting.