So I'm trying to lay down a drum sequence (I'm using Logic Pro / Logic Express) to John Mayer's I'm gonna find another you. I should say I'm adding an extra verse for a solo (just like in a live version).

Thing is, the song's tempo tends to vary. (And the fact that its in 12/8) doesn't help much), and I can't emulate any of the drums part without a metronome... What should I do?