Washing and letting the potato wet before wrapping in a paper towel was part of the instructions I got. If you don't use the bag, you prick the potato, wrap it in the paper towel, the steam from inside will help, I don't dry the potato either way. I wrap each potato separately if I put in more than one, just up the time a minute. Takes about two minutes for one medium potato in my microwave, saves a lot of time at our house.
Carol J.