As told to me and my wife by her oncology doctor on how to avoid exposing raw skin from a blister:
Thread a needle with a piece of sewing thread. Pass the needle through the blister to drain it and leave an inch or so of thread hanging out each side of the blister. Place a band-aid over the blister with the thread still in it. The blister remains covered by the skin, to reduce the chance of infection, and the thread wicks the fluid to the outside so it doesn't fill back up again and stays drained. Works best on blisters on the feet, but will work on blisters anywhere else too.