Dog anal glands question?

[Wintergirl]

When my German Shepherd was in the vet recently getting X-rays on her leg, the vet happened to notice that her anal glands were full from the X-rays and told me to give her Metamucil fiber. The only kind the drugstore had was orange flavor and she won't eat it, even when I mix it into her favorite peanut butter or a bowl of chicken broth, so I took her to a groomer because I heard they express the anal glands, and the woman there told me they only do the "outside" (whatever that means?). She said "we don't it like your vet." Well my vet told me use Metamucil - he didn't offer to do it either. What should I do? Is Metamucil enough to take care of it? She doesn't seem constipated and is pooping just fine.
She hasn't done the scooting thing and her poop is fine but now I'm worried.