My 2 year old dd is currently in hitting phase and its really rubbish, but my eldest two went through it and would never hit now (8 and 6) so Im confident dd will be fine too and learn to regulate her emotions safely.
Iv found- complete consistency, calmness & firmness, removal from situation every time, eg can no longer play this game its clearly too much for you, can no longer play with ... until you can learn playing nicely, etc in the moment, giving minimal attention for it just very clearly its not ok, hurting is never ok. etc. If seems like could go ok after a time sitting with me I may say ok, i know you can play nicely, your so kind with such gentle hands, shall we try a second chance at this etc.etc. So only when calm and they can then take in the learning.
Really important to manage the environment to remove potential stressers etc, if finding things too exciting and wild etc, or to chance where they sit if known to hit etc. And to notice when they are getting disregulated and respond before they get to hitting stage and help them calm down. Mine does yoga & I cant recommend that enough for helping calm, so when I notice shes getting cross/frustrated I can help her take her breaths and calm right down. Its such a helpful thing to do yoga, you could try cosmic yoga on you tube or get a toddler yoga book.
Watch Bing with them if you havent seen it, the episode called Tea Party where Bing gets so cross he pushes Sula so Flop helps him out is angry in a cloud by breathing and thats great.Theres also a great youtube video I think its elmo and Belly Breathe.
Ive just finished reading "Help your child deal with stress and thrive, the transformative power of self-reg" and that was really helpful.
We have an emotions board which I got from amazon to help them name & express their emotions and definitely talk it through, talk your emotions etc when they are calm. Thats actually helpful that they play it with toys as you can run with that and show them what you want them to do from that, and what happens when you hurt people etc (friends stop playing I mean).
I wouldnt use any way of getting out angry through hitting, Id use breathing and calm down etc. Gentle hands chat when calm etc.Lots of positive praise and attention when doing things well (oo you shared so nicely there, awesome sharing skills etc, or ooo I saw you were feeling really cross there and then managed to calm down etc etc...)
Its always helpful to remember its normal for kids to go through this.
Adoption UK may have some good resources too.
Sorry am writing quick due to having a 2 year old so apologies if too rushed and its kind of a monologue of what we do/have done, as i think, but may be completely not helpful to you & you probably do this anyway!