Just fight them unarmed and avoid throwing them into anything, as even bumping their head on a wagon or a rock seems to kill them, negating the trophy. My favorite convoy permaspawn point is to FTrav to the fort in the upperleft coner and just running down the main road and then fast traveling back to the fort to rinse/repeat my $ gathering efforts.
I, for one, welcome our new feral ghoul overlords! (call me PD -it's easier)
Personally, I get my convoys to appear by going from the town with a general store on the north west point to the fort back on the north west ... I havent tried warping directly to the north west fort and frankly, I believe it could work... Saving half the trip and making it faster.
The wind carried screams from the west. I could not help but smile - Kain PSN/MGO ID : Stealth_Cobra | MGO Character : Stealth_Viper