I have no idea how well they do with gay content, but I’ve used IAFD a lot to get at least basic metadata for 90s / 2000s era movies / DVDs.Matching performers to actual StashDB / ThePornDB performers can be painfull though, they really like to use first name only a lot.
For movies vs. scenes, it’s not really what stash is targeting, so it’s manual work in one way or another. I ended up with a process auto-generating split markers through a script of Stash Marker Sution, manually reviewing them (sometimes they are good, sometimes they are terrible), and then running a custom-made script to actually generate split scenes from those markers. Surprisingly, more than a few individual scenes actually matched through StashDB then (scenes sometimes get repacked so often, it’s hard to trace their name). But all in all, it’ s pretty custom, painful to get going, and not for the faint of heart.