Steve and Jess read Tim Gunn: The Natty Professor, and while it's not strictly about mentoring (and there's a lot of non-linear storytelling, gossip, and a few transphobic comments...) there are some really nice tidbits we can draw from. If you feel compelled to read the book, it's a very easy read, and if you're a Tim Gunn fan, he does read the audio version.