First, why are you even wanting to do it? Anal gland expression should only be done IMHO if a dog's anal glands are impacted.
For most dogs, the anal sacs are expressed naturally by the dog when it strains to poop. If your dog has frequently runny poop,or soft poop, then your dog is more likely to have anal sac problems, because the poop isnt' firm enough to push on the sides of the rectal walls and express the anal sacs. A food change can help this, as some foods don't encourage water absorption well enough by an individual dog (regardless of the quality of food (our Akita had issues with constantly soft poop while eating canidae, of all things).
i think its a pretty normal question. i myself, dont do it. when annie was scooting herself on the carpet, we took her in to the vet to have her checked out. he did express her anal glands, but they were fine. i think alot of groomers will express them. if your dog is scooting or emitting a foul odor, i would have him/her checked out. other than that, i wouldnt worry about it. its not something that needs to be checked unless you are noticing a problem in that area.
My last min pin we had Doby started scooting around on floor at a young age. At first the vet was expressing them about once a yr. But it ended up being more the older he got. Last few yrs we would have it done about 3 to 4 times a yr. And if you ignore it, and he's not doing his thing on his own. Than you will run into a errupted anal gland. Be prepared for sugery if that happens. I felt terrible when it happened to Doby.