The glands naturally express when a dog has a firm bowel movement. Frequently if a dog has loose bowels or diarrhea, the glands will fail to empty regularly. This will sometimes cause the glands to leak when the dog is not having a bowel movement or to become swollen when the liquid is not being released.
Since your dog seems to have an odor on a regular basis, it may just be that the feces are not firm enough to keep the secretions on the feces instead of leaking out on its own. What you can do for this is to give your dog a spoonful of canned pumpkin (not pie filling) on her food. This will absorb any excess water in the bowels, keeping the feces firm but pliable. This should help the anal glands express naturally.
If you look at the rectum, the anal glands should be located at the 4 and 8 o'clock positions, so you do want to start a little below that and press upward with a firm motion. Each dog is different, but that is the general location. I'm going to give you a few more sites to look at on anal glands.
The amount of fluid expressed can range from practically non to a tablespoon or if severly swollen you might get even more. The amount really depends on whether it is seeping out or being contained.
Since it does seem that your dog has problems with seepage, I would try getting her fecal matter firmed up and using baby wipes to keep the area cleaned of any leakage. Of course, you could express the glands regularly, but in most cases, expression is not needed all the time.
I hope this information is helpful to you.