Reggie actually had the same thing happen to him, with the yucky hole and everything. That was years ago. I didn't know anything about anal glands when it happened. He recovered fine.

I've expressed many anal glands on dogs (at work). It's really quite simple to do but it's rather messy and SMELLY. When you lift the tail you can feel the sacs on either side of the anus and just gently squeeze them. Of course it's easier to describe then do lol. Some dogs you can't feel the sacs because they are not full. Most dogs empty them on their own. It seems that small dogs and overweight dogs have a problem with it more often.

I've heard that emptying the sacs too often can cause the dog to not be able to empty them on their own. I'm not positive on any of these things though so check with a vet.