I think that if you know the way chords, any chords, are structured, finding harmonies really shouldn't be that hard. Start with the soprano who usually sings the melody, and work your way down from that. Once you get used to the way the melody is structured, you can phrase the harmonies around that.
I would say that if you want to structure harmonies on your own, learn how the chords are structured. Listening to the CD helps, but you can't rely on that.