This method is developed by J. Jenner. It is a combination of a CBT like intervention to teach coping strategies for voices and family work to support the person who is doing the training.
How to do it
Read his book Hallucination-focused Integrative Therapy: A Specific Treatment that Hits Auditory Verbal Hallucinations
The evidence
HIT’ is researched carefully: Hallucination Focused Integrative Treatment: A Randomized Controlled Trial, by Jack A. Jenner, Fokko J. Nienhuis, Durk Wiersma, and Gerard van de Wilige