This was all by ear, plus checking many videos for positions/techniques. Sometimes a live video might only indicate he probably played something differently, like crossing strings where there was an obvious slide between notes on the album, so that's something to watch out for during that step. The Naked Tracks and a few iso tracks out there helped too. Steve didn't assist on this one, but I probably could have sent a few questions if totally stumped on any parts. He did see my "Candle Power" transcription before it went up (at guitarinstructor.com) and suggested rewriting vibrato on a chord as a 1/2 step bend & release in the first measure. (I'm not sure how much time he spent looking through the rest of it.)
There are exceptions like Dream Theater as Lurker mentioned, where we had isos and emailed or met with Petrucci for every book (since Octavarium in 2005, plus his first solo album and probably the new one soon). Brendon Small helped similarly for all the Dethklok books. It's probably more common to not do this kind of thing, at least with larger publishers.
