Not Time Wasted

The gag reel for The Avengers DVD leaked this week, and one shot really pulled off an effect I couldn't get my head around.

In this slow-motion shot, Captain America and Thor retrieve their respective weapons. And although Chris Hemsworth is having trouble grasping the handle (the shot goes on to show Hemsworth bouncing Mjölnir between both hands), Chris Evans effortlessly slips the shield onto his right arm, pivots his torso while shifting the shield to his left, and throws a punch.

How did Evans handle the shield so perfectly?

Was it shot at him and he's just practiced for weeks? Seems like a quick way to break his fingers. Were there strings pulling from the other side? I can't imagine they'd digitally remove the wires for this outtake. Then I'm pointed to this shot (taken by a location bystander) from a different angle:

No shield. It's all CG.

So from my understanding, that means they had to

1) motion track Captain's body to know where and when his arms are flailing

2) manually animate in the shield (especially if he's moving the shield from one arm to another), because it's not an apendage to just replace (like an artificial arm)

3) texture, light and render the shield

4) rotoscope around Captain and Thor's body, for when they're overlapping the shield.

It's hard to believe a team of VFX artists spent billing hours and equipment pulling off this shot for a gag reel on a DVD, but then again Avengers is one of the highest grossing movies of all time.