I haven't read all of the responses but I have to warn people NOT to allow their groomer to express the anal glands as a normal procedure.
Your Vet. will tell you that it is not uncommon for dogs to come in with ruptured glands or other avoidable issues after their groomer expressed the glands during grooming. There is absolutely no reason that this should be necessary with a normal, healthy dog.
If your dogs anal glands are not normal and healthy, your Vet should be the ONLY one to deal with what to do about it.
I unfortunately forgot to tell my long time groomer (who was taught how and does it as a matter of course and had been doing it for almost 30 years) not to express Amos's anal glands and he ended up in Emerg. within 24 hours bleeding from his rectum. While she was expressing, she ruptured one side.....totally unnecessary and he was in HORRIBLE pain.
This is not something that needs to be done routinely and though your groomer may be doing this unpleasant service for you as a kindness, most grooming schools are no longer even including this in their curriculum. Too many things can, and often do go wrong.
If your dog is scooting and/or licking more than usual, often after having loose stools for a few days, then go to your Vet. This is not part of normal maintenance. I would absolutely never do it just because my dog is having a bath either.
I mean no offence to the groomers on the board but I actually lost a dog after an anal gland expression. My Vet. had to express her 'over expressed' anal glands, she had a seizure, went into cardiac arrest and died in my arms.
This can be VERY painful if done incorrectly and can cause lifelong problems....leave this up to your Vet.