There are a few things that may help with an anal gland problem. Keep your dog lean: overweight dogs tend to have more problems with their anal glands. Feed bones at least 3 times a week to ensure that some stools are hard. This will help with expressing a bit of fluid each time he goes to the toilet. Feed a high fibre diet eg. add pumpkin to meals.
If you feel that there is any component of infection in the problem, then consider using a course of blood cleansers.
You can also add crushed French White Millet to the diet. It is high in silica, an important mineral supporting tissue strength and health.