I am currently writing an MCC course for rotary-wing students, but same principle. The requirement is that anyone who has only single-pilot experience, but wants to obtain a type rating for a multi-pilot aircraft has to have training in multi-crew operations.
I dont have the paperwork in front of me, but off the top of my head, I think the minimum requirement is 25 hours theory and 20 hours practical (may be reduced to 10 hours if the course is integrated with type-rating training.)
The course is designed to teach the theory and practice of standard operating procedures in normal, abnbormal and emergency conditions, standard call-outs, division of tasks and responsibilities in the cockpit, crew decision-making, communication etc etc. There is lots of common ground with CRM. The full syllabus is available in an appendix to JAR-Ops 3 subpart N, which you should be able to find via google.
Some people who have spent many years alone in the cockpit have very poor understanding of how to operate safely and effectively as part of a crew - so this requirement is designesd to address that problem.