As someone who has anger issues, I've been to group sessions and one on one sessions. I find the one on one the best for me without sounding stupid the people in the group therapy sessions just piss me off too much.
I go and speak to someone once a month now It took me about 6 months before I could learn to trust that person and talk. But it does help, I use it to keep myself in "check" took about 3 years for to get the courage to admit I had a problem and went to go get some real help. I've broken laptops, smashed up walls and doors (we can only have hardwood doors in our house) once I flip I'll break my hand before the door breaks now. I've never hit my partner and never will.
My biggest issue is was understanding that I feed off the anger so ill keep looking for anything to keep me going and pumping me along for the next burst I feel like a fucking god when I'm raging nothing will touch me, I don't feel anything I want to keep that anger flowing for as long as I can and for me that was my biggest issue as to be honest... I don't want my kids to turn out like me so that's whey I choose to go and get some real help.
Now all the people doing martial arts or saying to go and do it. OSU. I'm a long time Kyokushin guy over 25 years behind me, I've done boxing, kickboxing, Muay Thai, Silat and more and to be honest it doesn't work - yes it might give me something to channel into it but if anything its made my anger worse as when I flip off I know what to do and how to lash out at things and people.
I can go from zero happy to smashing someone over the head and back to happy in a second and not be bothered by any of my actions and that's what using martial arts to control my anger has done.
The only good thing to come out with being angry and doing martial arts is that I've learnt most of what you are taught does not work when you are raging like a prick or want to be restrained so much so I teach a non compliant self defence system which is all about trying to cool someone else, defend your self and function when your being spat at, shouted at, hit and have all the emotions that come along with it.
Counting to 10 does not work for me.
Writing stuff down in a book about why I was angry, my triggers and what level I was at during that time because... that used to piss me off.
I garden a lot which can help chill me out. My biggest thing recently is I've discovered I have a wheat allergy since I've cut wheat out of my system my mood has improved a 1000% Id never have connected the both I'm still angry but now it feels like my fuse as a 2 second longer timer than it did before.
The biggest and best thing I have found is when I'm having an outburst my wife grabs me and hugs me and in about 8 seconds I'm calm and I'm back to normal.
My best advice for you and something that cost me 100s in therapy is to try and figure out what your triggers are and then work on them.
Good luck with it. If you need to talk PM.
EDIT
Part of having anger issues is admitting it, if you can say to your self you have anger issues without blaming something else or someone else then I'm not 100% sure that's a problem. it may very well be. I know everyone is different.
For me my anger was and is an addition it took me a very long time to admit I had a problem I've been arrested over it, been to jail over it, had issues with the police, family, friends and everyone else but it was never my fault. (in some cases its still not!)
As I said it took having kids. Mainly a son I hope never turns out like me.
Speak out, seek help. Get it under control.