When I was playing dying light with friend we discovered that every timw you go to sleep and wake up air drop will appear, if you don’t know air drops are pretty rare and if you collext them and deliver to one guy you will recieve lots of xp, we used that multiple times to unlock grapling hook very early. Air drops also gave lots of medicine which was hard to get in early game and that very helped us
In dying light theres also a way to farm the volatiles/night hunter before the mission to chase Rais or before the sewer run. You do this by going on a night run, alert some volatiles then run in a fast pace and do some parkour normally (this is a great way to level your stats if you dont mind getting raced and chased)
Once you’re near a river wait for them to pounce at you or lunge at you, if you’re good enough a simple side dash can mitigate the damage but ive found letting them hit guarantees they’ll fall into the water and just die. (Bring lots of meds I brought around 10 with enough to sideboard with materials before doing this) Once they fall over thats boom instant I think 500 to 1k exp per death on them I havent played DL1 for a long time so idk if they patched this out but it let me get the finisher and drop kick perk very early on. And also silent executioner.