Hi
I tried this today on Nexus 7 2012 to try and quicken tablet after Lollipop recd OTA. However, I only managed to get as far as :-
"6. While pressing and holding Power, press the Vol Up button, then release both buttons. You don't have to hold either button down for very long. The Recovery Menu will now appear:"
The screen just went black, no menu came up. I managed to power up but no cleaning of cache was done.