If you don't understand the cause of your anger you will never be able to control it. It's obvious you know your inability to talk about your feelings is associated with your anger, or else you wouldn't have mentioned it. Talk about your feelings- but don't do it here.
I wish I could tell you there are quick fixes like 'counting to ten' etc. But the truth is you have to get used to the feeling of being on the edge of loosing your shit, and you have to get used to sitting on that feeling. Retrain your mind to enjoy the feeling of suppressed anger, more than the feeling of released anger. It's proven that people have a natural tendency to become addicted to their own anger. You have to view it as a bad habit you are trying to quit.
I don't recommend becoming so severely apathetic that you no longer care to react, but if you already struggle with apathy you may use it to your advantage as well. I'm by no means a psychologist, and I don't know the full extent of your issues. It may be dangerous for you to hold back your anger.
I view anger as an intuitive symptom of when your mind knows something is not right. So it is important to recognize when you are angry and the truest cause of it- usually personal. That anger is trying to show you something. Perhaps something isn't right with a relationship you're in, or something isn't right with your own behavior and you don't want to admit it. Pride will always stand in your way when working through these kinds of issues.
Anyway, good luck.