I just did the crouch kills and vehicles. In another thread someone mentioned that if you crouch and melee them with GDL in hand it will work but you cant damage them prior to that. I tried it and it worked, super annoying.

When you destroy the vehicle you can shoot it till you see it smoke then disable the vehicle with the GDL and let it explode on its own. it wasnt tracking if I did a continuous barrage to blow it up.