This doesn't require the grappling hook but it's a lot faster with it. This guide is more of a mop up if you haven't got the achievement by the time you beat the main story.
To start off you're going to want to unlock the Safehouse on top of the apartment buildings in the western area of the slums that way you'll have easy access to a store and a bed.
Now what you're going to want to do is sleep till night and after you wake up simply walk forward and use the zipline in front of you. Once you reach the bottom you're going to want to shoot any gun you have to make a noise so that the volatiles come running then simply run to the lights and activate the trap, Rinse and Repeat as needed.
Also a side note if you're running low on ammo there's a store in the safehouse where you can replenish your supplies.
Here's a video guide if you'd prefer that: