If you have D-Dog with you he marks every human within like 300 feet, you should easily find most of them that are in the wilderness just by running around. Prisoners held in camps can be found by interrogating soldiers at those camps. None of them randomly roam, they follow a set path.
I have fully upgraded fulton and a rocket launcher that two-shots the APCs
CGM 25 takes them out in one.
Isn't one of the objectives to extract most of the vehicles anyway? Just park your horse in the road, sneak up and bag 'em. Or use the mine that stuns them if you want to be lame. You have enough ammo to shoot the few you are allowed to assuming you pick up the weapon being transported.
My strat for that mission was:
- immediately take out the 4 guards chasing the prisoner (I ran through them all from behind with the horse, stunning them and then extracting).
- ignore the prisoner who just waits, go north and shoot the vehicle before it leaves
- Extract the prisoner on the river
- Shoot the next target from around the small bridge in the center of the area at long range as it appears coming down the road
- Stun and extract the vehicle transporting the prisoner
- Sneak to the north of the main camp (go slowly and take cover to the side of D-Horse), then camp out around that corner since everything goes past there.
Then when all that is done you can take care of the rest of the prisoners.