There is no other way to attain Nibbana or getting of anger, depression or any hindrances than those 2 things.
1) Anicca nature for permanent results
2) Satipatthana and Anapana to clearly contemplate point 1.
Why we get angry? Because thru anger we want to get what we want because we think it will make as happy if a person will be that way or situation of life we want to be will be like that we want. Those ideas are ridiculous if you really close to it. Thanks to Buddha Dhamma, Lal and other people that I can be free to the very big extent from a self-created drama by ignorance.
Being angry at someone is that you believe in ICCA in a personal relationship. Nobody will make you happy EVER and nothing will make you happy ever, paradoxically understanding this will make you into something beyond happiness and unhappiness. Is the same pattern, the same way, and one direction but manifestation of ignorance seems endless.
Remember to go gradually, do not worry that you are getting angry if you do not feel that you leap over into Sotapanna, you need to know how to root out every fetter and this is only known to Ariyas on at least Sotapanna level.