I wanted to wipe my cache partition via recovery, and this is what it took to get into recovery:
Power Down the Nexus 6P
Boot the Nexus 6P into Fastboot Mode
Once in Fastboot Mode, Press the volume Down Button Twice
This Should Highlight the ‘Recovery’ Option
When ‘Recovery’ is Highlighted, Press the Power Button to Select This Option
This Will Take You to a Black Screen with a Green Android Laying Down
From Here, Press and Hold the the Power Button, Then Press the Volume Up Button
When Done Right, You’ll Immediately be Taken to the Recovery Mode Menu