You shouldn't question yourself, you shouldn't question why you feel angry, but it is very useful to question why there is anger in the first place. If you do this you'll see it's always coming from a sense of self, you either want to prevent something, change something, correct something for you think you will be better off. So don't look at the shallow end like "he said this but it was like that and therefore I have all reasons to be angry" or whatever, no not like that. Instead, look deeply, why does anger arise in the first place? What do you want to get get out of it? If you look deeply you'll see you also get angry because you like being angry.. Anger is also an attachment sometimes.
So I'd not say it is that much about watching anger rise and fall and how it feels, but really get to why anger arises, and how can you overcome it skilfully, and how to prevent it arising again in the future.