Grooming your dog can be a time consuming activity and sometime irritating to your dog. Grooming is also physically demanding no matter what size of dog you have because of the positions you may need to get into to groom properly.
One thing you can do to reduce your dog's and your own stress is to groom whatever is most convenient or accessible.
For example, if you have decided that you want to groom your dogs tail, and she is lying on one side (and is a large dog) you can groom one side of the tail. While you are there, you can groom a couple of paws as well, not trying to mold the dog into a certain position.
It's just easier that way.
Even though all my dogs are used to being groomed, I don't always follow a certain pattern during grooming.
I just do what I can and if I don't get done I leave it until a later time.
So the point is it is not necessary to really worry about not getting it all done at once and perfect. Just groom. Actually, MORE grooming sessions are beneficial to fewer, so if you don't get done you can do more later.