Anal glands are always a stinky issue.  Some groomers do them, some do not.  Some vets do them, some vets tell customers to have their groomer do them.  First, we need to understand the anal gland.  In large dogs anal glands are internal and should only be expressed by a vet because they have to insert a finger in the anus to express the gland.  No groomer should ever express internal anal glands.  
Over time, as many breeds were bred to be smaller and smaller there was no room for the anal glands and so they were pushed outside the dog’s body.  They are easy to feel for, they feel like peas on the lower side of the anus.  If you feel them they usually can be expressed.  If you do not feel them, do not express them as you can damage the gland.  It takes a bit of practice to know how much force to use to express the gland.  Use this link to learn the particulars go here:  https://www.akc.org/expert-advice/health/how-to-express-dog-anal-glands/
Many times I hear from a client that they think they need the glands expressed because they have a horrible odor.  If they have “blown” their anal glands the odor is terrible, however that also means that the gland has emptied.  The one thing that gets rid of the foul smell is alcohol.  
I don’t want anyone to confuse a “blown” anal gland (one that has just emptied on its’ own) and one that is ruptured.  A ruptured gland looks like a volcano crater on the butt.  These must be addressed by a vet.
Here is a great site for additional information on Anal glands:  https://dogcare.dailypuppy.com/color-liquid-supposed-anal-glands-dog-6031.html