| In most cases I load up a dark gray screen with a little noise so there is a significant contrast between the face of the phone and the screen. It’s just an image created in Photoshop. I then use Mocha to track and extract the reflections by blend modes from the original screen. A little noise reduction and I’m usually good to go. This works much better for me than trying to get reflections off green.
I also almost never add tracking dots. Mocha doesn’t need them and they are just things that need to be removed in post. The last time I used tracking dots was for a green screen project were we had no details on the set without trackers. | 
