Below is another video that gets into the visual effects of the The Hobbit: The Desolation of Smaug. It acts as an overview of not only creating Smaug the dragon but also all the effects that were used such as in the barrel escape.

VFX of The Hobbit: The Desolation of Smaug. There are any VFX of The Hobbit: The Desolation of Smaug in here.