Ahh yes, I had forgottern about Fred Picker. When I got interested in large format photography, I read Pickers books and subscribed to his newsletters. Other excellent sources of information on technique were Ansel Adams books and the article written by Howard Bond.
Picker was, I believe, first and foremost, a salesman of his products. He was always opinionated (what salesman isn't) but henerally had some good ideas and a fairly sound basis for doing what he did. If you run across his books or, better yet, a set of his newsletters get them. The information in them is timeless.
Another good source, especially for the technically inclined, are the articles that Howard Bond wrote for the old Darkroom Photography. I don't know if Howard still gives his classes or not but the articles used to be available at the classes.