500 XP, Nail Hammer
Talk to Trevor after talking to James during the Knockin On Heaven's Door quest to start this quest. Follow the mini-map out to the jungle and the flares are located at the red flags on your mini-map.
The only hard part is the Thug zombie, but if you kill all the other easy ones, he should be pretty easy to avoid.
Note: If there isn't a path on the mini-map back to Trevor after you get the flares, select a different quest then re-select this one and a trail should appear.
Bring back the flares to Trevor to get your reward.