I just stumbled on this video by accident. I've never heard of this instructor and his english is not very good, but I think he does a good job explaining and demonstrating internal martial movement.
He also clearly shows differences between movement in "external" vs "internal" and correct vs incorrect movement from an internal point of view. I think his punch at 23:00 is a good internal type punch (from dantien):
I could be mistaken, but to me it looks as if he knows what he's talking about. I think the whole video is worth viewing.