[anonymously]

The best thing that you can do for a dog that has a tendency to have impacted anal glands is to learn how to express them yourself. Check YouTube for how to videos.
Have your vet tech/vet go over how often this needs to be done for your dog (once a week?)
With the right diet, exercise and routine care, you may find the condition will clear up quite a bit and you may not have to express the anal glands as often…if at all after a while.
Make sure he is drinking adequate water, maybe add a splash to his meals.

Find a food that will give him firm stools, rather than mushy (less likely to get clogged in the anal glands).
Also, some dogs have better stools on canned food, others do better on kibble. Buy small amounts of the recommended foods and see what works, sometimes it takes a week or two to see a difference.
Plus, feed only once or twice a day, don’t leave food down.

http://www.vetmedclinic.com/?p=290 excerpt below
Prevention:
Expression of the anal sacs every few weeks or months often will help prevent anal gland fluid from accumulating and becoming thickened again. High fiber diets have been shown to help prevent anal sac disease in at-risk dogs, especially those that are obese.