An article freshly updated @ Android Police:
[Update: Nexus 6 and Nexus 9 Wi-Fi Security OTAs] [Flash All The Things] Android 6.0 Marshmallow Nexus OTA Roundup
[Update: Nexus 6 and Nexus 9 Wi-Fi Security OTAs] [Flash All The Things] Android 6.0 Marshmallow Nexus OTA Roundup