On the opening of the map where it shows a transparent red spreading would you create the growing red transparent area over the map in the Pacific with transparent shape tween. Also any tutorials on doing this.
Or would I use a mask to uncover the highlighted area.
They have drawn the red area and then used a circular mask to reveal the area. You can see that it starts as a small circle in the "middle" of the red area and as it expands parts of the circle reach the uneven edge of the area. So it tweens a small circle to a big one, which could be a shape, motion or classic tween as you needed.
However if you were doing something to say indicate the direction of grown/expansion you might want to just do a simple directional swipe.
As for tutorials, any one of them that shows how to mask a clip would work.