I just have some empty phrases for that purpose, like "It's going!" or "It sure is a day!". Feel free to combine with facial expressions that are difficult to interpret for maximum confusion.

Thing is, it's smalltalk. Smalltalk serves a purpose and it's not the acquisition of information, so your concrete answer is kind of vain.
Smalltalk is rather for getting an emotional feel for each other. It's the first step towards any sort of interpersonal relationship. And it can also lead to deeper topics, but it doesn't have to.