You take a TRE from another aircraft and let the factory train him in the tech side and let the test pilots fly with him in the sim. There's no great magic to being a trainer, just a lot of study! Training on an A340-600 isn't significantly different from training on any other aircraft.
David, are you anything to do with JustFlight or Phoenix? I have a few comments that might improve the product and a few suggestions for some spin-offs.