I've done some work with RSE workers over the years and have found either working with the existing pastoral care team and the people in the crews who are viewed as leaders seems to work the best. It's really not that much different to any work crew - identify the people who hold mana and are respected by the worker group and focus on empowering them as a way of delivering information and messages. Educate yourself about cultural differences, particularly around communication and how different groups perceive management - a number of cultures are very uncomfortable raising issues upwards. Take training outside and into the worksite, not in meeting rooms and workspaces. Use simple visual guides like pictures of correct PPE and simple flow-charts for processes and SOP (again with pictures).