DBT can help a lot with symptom management, and is a good starter therapy for CPTSD for this reason, but EMDR and inner child or schema therapy will do a better job of addressing the root cause of a person's symptoms.

It's unfortunate that there isn't a one size fits all treatment for stuff like this, but at least stuff like inner child therapy, DBT distress tolerance skills and journaling are all pretty helpful for me at this point. I'll take what I can get. (I went through DBT like 8-9 years ago, but I started seeing a trauma therapist in October.).

I personally found the ABCDE theory from Rational Emotive Behavioral Therapy to be helpful as well. The basic idea is that a lot of mental health issues, grief, trauma, etc are caused by our reaction to or our beliefs about certain events in our lives; so if we change how we see those events, we can eliminate the problem. It's at least been very helpful for me in terms of reframing stuff that's happening now, and putting it into perspective.

Emotional accounting can also be helpful, but for some reason journaling has taken over this skill for me. I was never really able to make it the consistent habit that I wanted it to be.

Disclaimer: I am far from healed, or even doing well, but I'm doing better and this stuff is a large part of why.

Edit: I also went through a CBT workbook for PTSD, and that also helped a lot with symptom management.

Edit #2: to clarify about DBT -- it's helped my self esteem and self image a lot, but it has never been able to do much once I get triggered and that switch flips in my brain that takes me back to my past. I still use DBT techniques for symptom management, but they're not my only tools.

I think it helped me a lot, but what's worked has been kind of ingrained into my behavior, and what hasn't worked has been dropped. I still think that it isn't going to be as good as other therapeutic modalities to treat the core issues behind CPTSD, but your mileage may vary.

If someone has CPTSD, they should see a trauma therapist; and someone specializing in trauma will be able to help you go in the right direction. For a lot of people, DBT is at least a pretty darn good start. It is 3:30 AM and I am probably contradicting my own earlier points.