When you catch your dog dragging his behind, he's not using the lawn for toilet paper. His anal glands are full, and he is trying to relieve the pressure. Most dogs naturally empty the little sacs, located under the skin on either side of the anus, during bowel movements. Sometimes, though, for reasons unknown, the glands may fill up faster than they empty or become blocked. Emptying the anal glands will relieve the pressure and keep them from becoming infected and possibly bursting, an issue that would require surgery and antibiotics.
Put rubber gloves on your hands. Spread an old towel on a flat surface. You can perform this procedure on the ground, but if your dog is small, it will be easier to do on a raised surface such as a bathroom countertop.
Place your dog on the towel, standing.
Lift his tail to provide access to the anal area. It can be helpful to have a second person hold your dog's tail and help keep him still and calm.
Hold a tissue to your dog's anus with one hand, and place the thumb and forefinger of your other hand on either side of his anus. If the glands are particularly full, you may be able to feel them. A full anal gland feels similar to a ripe grape.
Squeeze your thumb and finger together, or inward, toward your dog's anus. The pressure should release the fluid from the gland onto the tissue. It may squirt or it may ooze. You can expect some to get on your dog. Use pet-safe wet wipes to carefully clean any of the matter off him.
Throw away the tissue, wipes, gloves and old towel when you're finished. Wet-wipe your dog's hindquarters again if the express job was particularly messy, then wash your hands.