I don't play reggae guitar. He heard the song once, went in and dropped it. He's a genius. It's found in patience. It starts in the instrument itself, but great-sounding instruments don't always go to tape easily.
Guitars sound different in different rooms, and certain rooms have a certain life.
You have to be sensitive to which room gives the song its strongest voice. My favorite room is the wood one in Grandmasters Studios in Hollywood. The guy building the studio tuned it from the front door all the way into the recording room, and it's just beautiful. The Black Crowes recorded Shake Your Moneymaker in that room. It's really magic.