Cut Out Shape with Animation

I want to do something similar to the following:

How to mask an image in IOS sdk?

I want to cover the entire screen with translucent black. Then, I want to cut a circle out of the translucent black covering so that you can see through clearly. I'm doing this to highlight parts of the screen for a tutorial.

I then want to animate the cut-out circle to other parts of the screen. I also want to be able to stretch the cut-out circle horizontally & vertically, as you would do with a generic button background image.