On OS X I run iTunes (126.96.36.199)
I keep going from iOS 9 beta 3 back to iOS 8.4 due to finding glitches. Because of this I have to keep waiting for ~20mins for iOS 9pb1 to download. Is there a way to download the IPSW so I can doit within iTunes to skip the waiting time?
To get iOS PBs I had to enrol my device by installing a profile. After I done that I then updated OTA via System > General > Software Update.