Application of sixteen contemplations in the anapanasati sutta

I've had a regular morning meditation practice (15 minutes or so, longer when I can) for about 12 months now, and I have a question about the sixteen contemplations as explained in the anapanasati sutta. The interpretation I have read is from the excellent Breath by Breath: The Liberating Practice of Insight Meditation by Larry Rosenberg. My question is really around how (or even if) I should be applying these sixteen contemplations in my daily practice. Should I be trying to work through each of them, using each contemplation as a basis for the meditation? Or is it more of an organic process than that (i.e. I will progress through them naturally with time)? Many thanks