If one just uses relaxation and self-instructions to reduce stress, then step one will be brief. If one tries to get insight into their negative thinking and learns many cognitive emotion-control methods, it may take many hours. Likewise, it will take much longer to deal with a 20-item hierarchy than to deal with one situation. The practicing of emotional control in fantasy may take 2 to 10 hours and about the same time for practicing in real life situations. Actually, it is unending because rational thinking and self-instructions will stay with you forever.
Some people have great difficulty believing they are responsible for their emotions.
Still other people can't imagine fantasies vivid enough to arouse the unwanted emotions. And some have trouble fantasizing how different techniques will work out. If the emotions are too unpleasant to voluntarily experience, start with less intense emotions in an hierarchy or seek therapy. This method is only 20 years old or so. The results are promising, suggesting about the same effectiveness as desensitization.