As you say, Slash mostly uses:
The Pentatonic scale
The Blues scale
The Major scale (ionian)
The Minor scale (aeolian)
The Harmonic minor scale
The Dorian scale

It would take weeks to transcribe that whole video, is there a certain part of the video you're interested in, for example "at 2:20 there's a cool lick"?

There is a really good app called Transcribe!, do you use that? You can get a 30 day trial and try it out. You can slow down, speed up, remove vocals, etc., and it works with video too.

That's what I would do - slow it down to 10-20% of the speed, and carefully go through each note until you figure out what he's playing. Sometimes that's the only way :).