You probably don't have to go through the whole power button procedure because it is assumed that the power circuit in the keyboard membranes is shorted out, but using just the battery connector method does not always work for me, and the full procedure always does.

Of course, this assumes your battery has a charge :-) You will need to reset your system clock after this procedure. At this point, try to start your Mac normally (this never works for me).

Hold the power button for another 10 seconds. Press the power button for 10 seconds, then while still holding the power button, connect the magsafe connector to your MacBook. The trick for now? Perform the power reset that you can find in many internet sources: Disconnect the battery and magsafe power connector. Now, this Mac won't power on either and I am awaiting a trace repair pen so I can fix it. Unfortunately, when separating the membrane layers, I was not cognizant of the Caps Lock key's LED attached to the membranes and damaged a couple of traces. I actually dismantled the entire keyboard and cleaned between the membrane layers to clear the shorting from the printed circuits. My daughter spilled apple juice in my wife's 2012 15' MacBook Pro.

Macbook pro 13 logic board power pads