Use the car mentioned in the video below, besides the multiple weapons glitch, but becareful there are some angles that enemy can shoot from (look at the metal door to your right after going prone), and sometimes juggernaughts may get stuck directly to your right and start to shoot you, this happens when there are three juggernaughts, or when there is a dog strapped with C4 about to explode close to the juggernaught, the juggernaught trys to run away from the dog, and he may get a firing angle, and sometimes some enemies may go rogue and just shoot at the car, and they rarely hit you, but there is a door in front of you that sometimes enemies stand near it -but mostly they'll just brace themselves by it- and they maybe able to shoot you, but remember that helicopters mostly shoot you (use video number 3 to avoid helicopters, but it requires a partner), and as you gone prone, you may not be able to fight back, however, this happens after the wave 30 I think, and make sure to detonate the car you'r willing to go prone on and the one besides it, because they may explode, for a reason or another.


Here are the videos:

1- The car invincibility glitch:



2- The multiple weapons glitch:



3- Another invincibility glitch (requires a partner):



Note: These videos are NOT mine, I just found them in YouTube, tryed them, and liked to share them by adding some tips.