I would not use Ellen Bass' The Courage to Heal. She is a poet, not a clinician. She also embraces the long since discredited "repressed memories." The net effect of that movement so popular in the late 1980s and early 1990s was that the courts began to doubt survivors based on expert testimony from memory researchers. Also, you may want to consider having different groups for survivors in different phases of their recovery. While different "schools" of psychotherapy differ on approaches, most of them agree that working on emotional regulation with survivors needs to be done before trauma processing. Some therapists will then work on social constructionist meaning making and existential spiritual, purpose in life concerns. There are a number of workbooks written by professionals that deal with these phases, though I would be careful not to "manualize" any approach. Therapy, no matter the modality (individual, group, family, couple), needs to be individualized and tailored to the unique situations of the people you work with. I would be trained in a number of approaches- CBT, EMDR, Expressive Arts Therapy, Somatic Experiencing, Sensorimotor, Narrative and Existential models of treatment and learn when each model may be the most effective with each client's individual concerns. This is not eclecticism, but an integrative approach where you are using intentionality when using any of the above approaches. The VA has an app that attempts to match the individual qualities of the client with the approach.
https://www.ptsd.va.gov/apps/decisionaid/