The intro should be done using NATURAL HARMONICS like this..
|----12-----5----------------12------5--------------------------------------|
|-12------5---------------12-------5----------------------------------------|
--12------------------------5-----------------------------------|
----------------------------------------------------------------|
----------------------------------------------------------------|
----------------------------------------------------------------|
~~~~~~ ~~~~~~
~ pretty wild vibrato - since this is a harmonic on an open string you need
to use a vibrato arm (or if your guitar does not have one you can do this
by applying pressure to the string above the nut - but this is harder
to control)