Jump start from the hood

The ground side is easy, just pick any clean spot on the engine block that is handy. The positive lead is a bit harder depending on the way your car is wired. Most need to be jumped using the same terminal on the starter solenoid that the battery cable from the trunk connects to. That is the only safe place to connect. That connection is also likely the reason you cannot jump start from the trunk. It has corroded and is not passing enough current to operate the starter.
The better solution would be to disconnect both the ground and power cables and clean them at both ends to get a better connection, then put a battery charger on it overnight. That is because if it cannot start the engine the cable is also not sending enough of a charge back to the battery.