Alongside his own work, Garry is fully involved in talent development and nurturing new writers and writing. He was visiting lecturer in screenwriting at the Northern Film School 1992-2002, and became the first lecturer in scriptwriting at Leeds University in 2003. This appointment led to him designing and launching the masters programme in Writing for Performance and Publication in 2005. He was its director until 2020, running the course in partnership with Leeds Playhouse in the later years.

Garry has led countless workshops and given talks and presentations on playwriting and screenwriting as far afield as the United States, China, India, Australia and New Zealand, as well as in the UK and various countries in Europe. He has run masterclasses at Oxford University, London Film School, LAMDA and East 15, and acted as advisor and examiner at numerous British universities including City University of London, Glasgow Caledonian, Swansea, Sheffield Hallam, York St John and Central School of Speech and Drama. He has published articles on dramatic writing in Studies in Theatre and Performance, the Journal of Screenwriting, Studies in Musical Theatre and Theatre Research International.

The many writers he has personally tutored include Jeremy Dyson (The League of Gentleman), the playwright and poet Zodwa Nyoni, and the Bafta-winning screenwriter Alison Hume.

His most recent mentoring work has been with scriptwriting groups connected to Cast in Doncaster and Sunderland Culture. He is in demand as a mentor to emerging writers holding Arts Council Develop Your Creative Practice awards.