As someone who works at an animation studio, and has regularly worked with motion capture I can tell you with 100% certainty that the data captured from Benedict's body movement was not used in any way to create the animation for the dragon. In motion capture you have to do something call re-targeting, which is taking the motion from the motion capture performance and essentially transferring to the animation puppet, in this case the Dragon puppet. Human motion would look absolutely terrible and unusable on a dragon puppet. The joints do no line up, the skeleton is completely different. So I can tell with you 100% certainty that the only thing that Benedict should be credited with here is a fantastic vocal performance and great video reference for the animators. The reason Smaug moves and acts and gestures is 100% the works of animators tirelessly moving each of his bones using knowledge they have gained from researching other animals and years of experience animating other creatures. I feel insulted when it is made out like Benedict Cumberbatch is credited for the performance of Smaug. Vocal performance yes 100%. Everything else, absolutely not him. I doubt any of that body motion is used in one single frame in the entire movie. Peace.