Having not read The Hobbit and falling very short of being knowledgeable about Tolkien and his writings, so much of what you wrote here was mystifying...in that good way that makes you start to wonder about things and be tempted to look more closely. For example, I just assumed that what I saw on the screen was what Tolkien wrote, and so I didn't worry about the forges and Smuag's powers of detection. I just drank it all in as canon and engaged in an act of pretty much total suspension of disbelief.

Having said all that, I will just agree with you that the gilding of Smaug was one hell of a glorious image to behold.