There are a number of ways of successfully treating PTSD, primarily through therapy, sometimes paired with medication. Some common therapies shown to help best with PTSD include CBT and EMDR. Research also shows though, that perhaps the most healing part of therapy is building a strong relationship with a therapist, meaning there is trust, support, no judgement, caring, knowledge, experience, and a long term commitment. For example, I'm in a more traditional psychodynamic (talk) therapy with some elements of DBT and others, and it works well for me.
The key to PTSD therapy, in terms of healing or recovering from it as much as possible is to deal head on with the trauma, working through the experiences, the senses, the feelings, directly until we can put them in proper context and they don't disproportionately upset us anymore. That's a very very difficult and often time-consuming process though. Other parts of therapy include establishing trust, understanding exactly how PTSD is playing out for the individual, and working on strategies to cope with symptoms, etc.
In addition to dealing specifically with trauma, he'll likely also be encouraged to provide some context about his life; his upbringing, personality, relationships, etc. So, it's a combination of focusing on openness and also symptom-specific treatment in many cases.
Therapy absolutely helps me open up again, for me, it's the primary goal, to be self-aware and open up to getting my needs met, being more myself, a better person, happier, and less stressed/upset.
What helps me most in therapy is trusting my therapist to know what she's doing, be there for me, and having, most of all, a safe place to tell my life story and have the support I need to look at it gently and critically, to see how I've gotten where I am and how to get where I want to be.
I hope it helps your husband! Therapy is emotional, hard work, but can be extremely rewarding in time.