in stepping out irregular hips/valleys ,would you step out the pitch that lies in the middle of your two pitches. Or would it be just as true to pull a string and get a measurement.
Also, where could i find a book on a framing square
There are several books available on roof framing. Just check online or at a large bookstore. I have a reprint by the Bureau of Naval Personnel on Basic construction that tells you how to build just about anything.