I am a mental health professional. Some people want a quicker fix than what your Process Model offers. Can you recommend a brief therapy instead?
Because forgiveness is a moral virtue, it is not possible to artificially push it into a traditional psychological set of techniques that might lead to quick forgiveness. If the injustice is serious against your client and the hurt deep within that client, then time and practice definitely are recommended. It will be worth the effort because we find that traditional psychological techniques are not a substitute for a true struggle to grow in this heroic moral virtue. A meta-analysis by Aktar and Barlow show statistically that longer periods of time in forgiving (12 and even more sessions) are more effective than short-term therapy of 4-6 sessions. Here is a reference to that meta-analysis:
Akhtar, S., & Barlow, J. (2018). Forgiveness therapy for the promotion of mental well-being: A systematic review and meta-analysis. Trauma, Violence, & Abuse, 19(1), 107-122.