DarkSky International now has a set of (very similar) instructions on how to submit a comment on the filings above: https://darksky.org/news/two-satellite-proposals-threaten-the-night-sky-the-window-to-act-is-now/
They provide templates to help get you started (but be careful using templates, it's my understanding that the FCC will only consider "unique" comments that are submitted). But I think having a large number of individuals who are willing to jump through all the stupid hoops the FCC has set up is a pretty powerful statement in itself! Thanks, all.