Haven't played (PS3), but to feed the dogs you have to kill a zombie near the red dogs heads on the walls, there is three of them. Once you kill a zombie the beast will come out of the wall. You feed it by killing more zombies until he is full and goes back in the wall leaving a red flame off the wall. Do this to all three beast spawn locations to get the Hells Retrever. I watched a couple of gameplays, I do not believe there is an actual power switch. You power up devices by entering "afterlife".