I have tried to keep this as generic and accessible as possible, but this is specific to me, my training and my thoughts around psychotherapy. Most art psychotherapists are psychodynamically informed, however weave other schools of thought into their sessions. Essentially, every psychotherapist has a different view and way of working, but this is mine:
From my understanding, there are three key elements to all psychotherapy.
1. Making the unconscious conscious. In simple terms, through attending psychotherapy we are made more aware of the difficulties/traumas we may have been through, and how they may be affecting us now. Everyone has endured situations that have been too difficult to deal with - resulting in our 'defences'. This can be difficult to grasp and make us feel vulnerable to talk about, but a good psychotherapist provides you with a space to work through these defences safely and without being judged. Within art psychotherapy, we believe that artmaking provides a less confrontational, and more direct, link to these unconscious processes. By making art in the presence of a mindful professional, and then have space to reflect upon this process, there may be elements of our lives 'projected' into the artworks we were previously unaware of. You can then work through these dynamics with the psychotherapist to facilitate you to make sense of them: it is important to know that psychotherapists do not 'interpret' or tell you what your artwork is about or what it means. The only expert on you is you.
2. Secondly is 'transference'. This is a psychological term referring to the feelings and types of behaviours that a person attending psychotherapy has towards their therapist. The relationship between psychotherapist and client can 'echo' previous relationships. For example, a person attending psychotherapy that has had a particularly harsh and restricting parent may find it difficult to open up to a psychotherapist through fear of what might happen. Similarly, a person brought up by a continuously sad parent could attend therapy and responds to sad topics with laughter and denial, in effect trying to cheer the psychotherapist up, as they may have had to do in the past. It is up to the psychotherapist to address this sensitively at the right time in order to discover what it might mean to the individual person. These are hypothetical situations and of course are not 'one size fits all' but simply an illustration of transference.
3. Perhaps the most simple and important of all, is experiencing a 'good' relationship. Good psychotherapists set boundaries, are reliable, and non-judgemental. Experiencing this can allow us to regress to past stages of development that may have been skipped or difficult, reliving them with a better ending. This can be expressing different emotions safely or being supported, but also knowing what to expect and predict reactions. In time, this relationship can then model for the other relationships outside of the therapy room and allow our own inner dialogue to internalise aspects of the psychotherapist.
There are many other key aspects to psychotherapy, but these are three simplified ideas that I believe are integral to art psychotherapy. Keep in mind that in order to fully benefit from psychotherapy, a person must be willing to engage and 'in the right place'. It takes a lost of emotional effort and often things will get worse before getting better - nothing is ever as simple as this, and the process of psychotherapy is often is a rollercoaster of ups and downs.