I have the book "Hurrell's Hollywood Portraits" by Mark A. Vieira and it describes a lot of his techniques over the years. His golden age lasted form 1925 to 1943. After that time the studio system was coming to an end and the formal glamour Hollywood look had run it's course.
During his time at the various studios that he worked for and even at his own studios his technique and equipment changed many times. The film was improving and he changed with the times. The one thing that he did practically invent was the "boom light" or at least a moveable boom. He used it in a lot of his portraits, heavily backlighting his subjects as well as using it to light their faces at times.
As good as Hurrell was, he is often given too much credit these days for the Hollywood look. There were a lot of great photographers during that period whose names are forgotten. Some are Clarence Bull, Bill Daniels, Frank Tanner, Laszlo Willinger, and many others.