Seneca or Aztec
I have had the misfortune to have to use the emergency gear system on both types in anger. The simplest is the Seneca as the gear is held up by hydraulic pressure and operating the emergency gear lowering knob simply dumps all the pressure out of the system. It is important to ensure that the airspeed is low as the nose gear retracts forward and is assisted in lowering by air pressure. The Aztec nose gear retracts rearwards, so it needs assistance. You have to slide the left-hand pilot's seat fully rearwards and it uncovers a panel in the floor wth a butterfly nut. Removing the panel exposes a ring and cable attached to a gas cylinder that provides the pressure to help the gear down. You pull the ring, but there is no obvious reaction and you have to glue your eyes to the mirror on the left nacelle. After an interminable time you will see the nose gear appear and eventually lock down.