It's just camp in the tunnel, make sure you're able to survive and kill shotgunners when they come in by using Survivor Link, and use Survivor Link to place the bomb. The bomb wave always has shotgunners except for the last wave but you don't need to kill every enemy in the wave before placing the bomb, so you just need to survive the shotgunners, kill any snipers and drones, kill the bomb carrier, clear a path on either side towards the APC, get the bomb carrier to the switch, turn off one turret to make things easier, use Survivor Link and set the bomb and then run back. As long as at least one person survives when the bomb explodes then everyone on the team revives so it's all about being able to survive hits, kill enemies fast and move optimally. The worst thing to do during the bomb waves is just doing nothing in the tunnel after the shotgunners are killed because the enemies will respawn.
