I tend to agree that teaching facilitation skills via distance learning is problematic. travelerjjm has it right; teaching people the same format that they are expected to deliver it is ideal.

If travel is an issue and they need to learn how to facilitate in face-to-face training sessions, then video-conferencing is the next best thing. Make sure that the video equipment captures the facilitator and the audience so each group can see each other clearly.

The other option is to employ(contract) a local facilitator for the group to deliver that piece of the Train the Trainer.

Good luck with your facilitation.