You are probably familiar with Bob Staake's work even if you don't exactly know him by name. As well as a series of iconic New Yorker covers in recent years, he's responsible for an astonishing run of childrens' books (often writing as well as drawing) alongside copious illustrations. His books feature gorgeous endpapers and the kind of attention to finish that I wish I could emulate - hopefully one day I will get there. Bob is very open about his process, if you follow him on Facebook he drops all kinds of anecdotes and insights on a daily basis. To the best of my knowledge, he still uses Photoshop 3 to generate his trademark style, making a mockery of the "upgrade curve" - as the video below displays. There are a number of videos of his technique if you search for "Bob Staake" on Youtube.
I honestly believe that among working illustrators, Bob is peerless today and an example to anyone who wants to see how to do the job right. Here's his website!