Use vehicles.
1) If you upgrade your Rebel Ops so that you can request a Helicopter on demand, or know which safe houses have helicopters, they are the best way in my opinion.
Just fly above the convoy, position the side of your helicopter that has the 2 gunners pointed at the convoy, and then order attack.
By just maintaining a decent chopper path around the convoy, your AI gunners will take down the trucks and eventually the convoy vehicle without too much hassle - more often than not the convoy vehicle stops well before having it's health eliminated.
2) Rely on vehicles. The heavier, the better. Ram into the rear vehicle while ordering assault, will take that vehicle out quickly.
At that point, focus fire on the convoy and it'll stop quickly. The lead defense vehicle always seems to drive way off into the distance.
Doing anything on the ground as a foot soldier, relying on explosives, leaves too high a risk of you killing civies or blowing up the truck itself.
1 people found this helpful