One of the best ways to learn how to groom a dog is by having access to some really good dog grooming videos. That way, you can play them over and over again until you get the various clips down pat. Or, you can simply replay the sections that you need to review until you are totally comfortable with the various clipping tasks.
There is no substitute for professional instruction when it comes to a practical skill such as dog grooming, particularly if it is complemented by comprehensive dog grooming video footage.