Easiest and fastest method below :- grab a buzzer (you can buy one at your home)
- fly from outpost to outpost
- land on a land above/higher than the outpost and avoid to be detected,
- leave the buzzer,
- scan the enemies with your camera (optional but make next step easier)
- spread a lot of rocks on the outpost
aiming above due to gravity,
- wait ~30 secs (it looks that it register "distracting" after 3/5 secs as the achievement unlock form me ~3 secs after I trow a rock, 30secs are for safety
).
- fly to another outpost,
- rince and repeat.
It should take 3 or 4 outposts (the first smaller ones are easier).