AE's film grain can take a long time to render. It's often faster overall to create a 1-minute clip against a gray solid and then apply that layer as a looped overlay on any footage you want to add grain to.
Cool. I'm on Premiere so I'll definitely look into that.
After Effects has a pretty good filter for this, which was a separate product before (Grain Surgery). Apart from some good presets, it can analyze scanned footage for grain and reproduce that into your own. It is used quite a lot when CGI needs to be matched to analog film.
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