Hey Justin. The situation you find yourself in is not uncommon. Ideally the screens would have been turned off and you could blend the original reflections back on top of your comps. However, if you’re creating them yourself it can get very tricky very quickly.
Your case is particularly tricky because the viewer can compare the true reflections to your fake ones as the device/camera moves. The plus side is that you have a great reference as to how they should look. Depending on how sharp and close up those true reflections are will make all the difference.
What I do to recreate botched reflections is to simply use feathered white solids.
1) Duplicate your preComp (the screen) in your project panel and in your composition, then drag/replace the duplicate layer with the duplicate in the project panel. Now you have two unique copies of your screen in the composition on top of each other.
2) Inside the duplicated preComp (topmost), delete all the layers and create a white solid (as reflections are typically white/lights). Now add a very feathered mask to it (you will customize this later).
3) Back in your main comp, lock the viewer by clicking ‘toggle viewer lock’ at the top left of your composition viewer window.
4) Here’s where things can get tricky.. You’ll have to animate & tweak your white solid to move and look as close as possible like your true reflections. Of course you can use any type of layer you want for this but in the end it’ll likely only look better, not perfect.
I’d love to hear other user’s tricks on this one.
Mike