Normally I would echo the idea of books over video but not so much in this case; first hand experience is always best but video will do. Steven's Magic had a nine part series I believe it was, on Pick-Pocket work about a year or two back, you may want to touch base with them and see if it's still available (you could buy it one lesson at a time). There's some other material out there and if you can read French, I believe Majax put out a book back in the 80's, and he was absolutely awesome. . . his work as a Pick-Pocket and magician made him the French equivalent to David Copperfield for a couple of years.
Ricky Dunn put out a book a few years ago but I know that a huge part of his original act was based on the Kirkham act (they came to physical blows a few times because of it). I'll warn you however, if he comes clean on this point he'll have to tell you that there's a very big cheat involved that's been used for generations by some of the biggest names going. It will certainly surprise and more than likely disappoint you (as it does most).
Needless to say, there are dozens of You Tube fools teaching this, hypnosis methods, and 1001 other things for free should you be willing to endure the pain of watching them.
