Potato Bags
Our craft group has made these to sell at our Church bazaar for years, with no problems. The instructions say not to prick the potatoes....maybe to keep the juices from escaping? Also, with newer microwaves, it's best to start with 4 minutes of cooking time. I've never heard of wetting the paper towel either.
This year, we also made "corn bags". A larger version of the potato bag and made with "corn" fabric, of course!