Try learning the song in sections using Riff repeater, and then ignore the notes coming down and just play to the music, only use the notes as a reminder of what riff you should be playing.
For riff repeater use Leveler until you level up to a part where you can't get past, then use Accelerator to slow down the part you're having problems with.
Though... with Leveler I wish that you could tell it Level Up / Level Down a section even if you haven't hit all the notes, and with Accelerator you could tell it to play at a specific speed rather than it "calculating" the speed for you.
