re: FYI - The ISS is flaring
An Iridium satellite has a rigid solar panel arrangement and a fixed attitude in space relative to its orbital path, so figuring out when the light will bounce "just right" for a flare is a matter of math, but the ISS has panels that change position constantly relative to the station so predicting flares would be much harder. Note in the movie that only one set of panels flares, even though ideally both would be pointed toward the sun.
If you catch one, it's probably a matter of a lot of luck.