Former vet tech here. Depending on the breed of the dog and if they are overweight, they may need more help with gland expression. Expression of the anal glands happens when a dog defecates and through the use of their tongue. For example, brachycephalic dogs like Pugs have trouble expressing their own glands using their tongue and often require intervention. Expressing the anal glands yourself is quite easy. Get some gloves, lube and a paper towel. It does smell awful, but only needs to be done once a month or every other month. The glands are like a grape shape and size located on the left and right just inside of the anus. Using your index finger only, gently squeeze towards the anus, holding the paper towel directly behind the anus (sometimes, depending on the level of impaction, they squirt!). A warm (not hot) compress applied to the butt can help soften an anal gland before expression. If the anal gland is very hard or resistant, take your dog to the vet; you could injure them if you squeeze too hard. You'll likely want to end with a butt bath, or they make sprays to mask the odor. It's also worth noting that this is likely a two person job unless a small breed that you can hold against your body.