From a personal point of view, the whole process was a remarkable spiritual experience. To spend such an extended time immersed so deeply in a text of Scripture was a wonderful experience, and a number of my writing weeks offered me a profound sense of being in the presence of God. I hope to repeat the experience in future commentary writing.
— Read on www.psephizo.com/biblical-studies/what-is-it-like-to-write-a-commentary/

Here is a wholly enjoyable read from Ian Paul on his writing of the rather new volume on Revelation in the IVP OT and NT commentary series.