Need help from any Campy riders...

[Seajay]

Or is the thumb button used for shifting in one direction, and then the shift lever moved .
Correct. Right thumb is an Upshift. Left Thumb is downshift.
Right Lever is Downshift, Left is Upshift.
When new, I think the shifting is a tad stiff. But very positive at the same time.
That said, you might try to ride someone's Campy before you invest to make sure the size of the levers, action and lever pressure work for you.
I'm a big fan of Di2 because it solves so many of these issues for smaller hands.
My 2c