looks like this mini guide's pretty useful lol
Terminal - Right at the start, switch out ur striker shotgun for the akimbo desert eagles, (for faster sprinting). Once u run out of the cubical thingy the level starts, so start sprinting to the stairs and run across the edge of it, right next to the escalators, then hop the rail. Run n jump over the seats right in fron of u once u turn right after hopping the rail. (basically, throughout this ops, u just run and jump.) run around the little tree in the middle of the room, and dodge all the attacking soldiers and run into the doorway, and run across the whole restraunt/library/whatever, and then hop the rail again. sprint into the library and then exit the other side, and run down the esclators, and probably throw a flashbang down it before u go down if ur unsure. once at the bottom of the esclators, turn a hard left and sprint the last amount of juice u got and finish this ops for 3 more stars.
High Explosive - this one is veeery easy with 2 people, doing the cheat. right when u start, jump over the wall after u turn around ur spawn point, and run all the way to the back. the building is pretty close to the motorcycle, im not sure where tho, but it's to the left, if u down the middle of the map. just leave 1 player in the doorway, letting him get downed by the juggs, and then the downed player will knife the juggs till they die. This ops will take about 15-20 minutes, depending on how good the knifing player is at knifing.
Homeland Security - I suggest doing this on ur own, due to the fact that with 2 players, u get less time between waves, and the foot soldiers are a lot harder and smarter with 2 players. Right when u start, pick up the sentry gun, disregard everything else, and sprint to the Nate's Resteraunt and situate the sentry towards the gas station, and by now the first wave should start up. If ur a run n gunner, go ahead and pick up the other turret on the restraunt roof and just run to Burger Town, occasionally dropping the sntry for quick kills. Situate this sentry also towards the gas station. After this, u can choose whether to just camp in the ruined building between the restraunt and the burger town or nab the 3rd turret from the bank, right from the restraunt, (if u were facing towards the gas station.) This turret is almost pointless, due to the fact that just getting there will probably get u killed, since that area is a blind spot for the sentry guns. Just screw the 3rd turret and camp with a thermal M21 EBR and the default scar-h assault rifle. Just sit tight in the building till u reach the round with helis, then u will be forced to go outside, to either nab the stinger/rpg/at4 or to alert the predator drone and maybe get lucky. (i recommend going for helis and BTRs after all the footsoldiers from that wave is gone. This op will take u roughly 20 minutes, if u follow this correctly. (this is also fool-proof, by the way)
Breach & Clear - for this level, just go with ur default guns, and when u breach just kill every1 in the room as always, then pick off rest of the people, then after that, in the second room, start throwing ALL your grenades and ur only flashbang at the next room, because a lot of roitshield ppl and regular soldiers will spawn from that room. Once u hear the flashbang pop, sprint all the way to the hole, and if u want to make the drop definite, zigzag and jump to the hole.
Armor Piercing - Once this op starts, run up the first small set of stairs and pick up the .50 cal for either gun, doesnt matter, then sprint all the way up the flights of stairs till u reach the scaffolding outside, (the elevated area with the blue tarp behind it). This is where u will spend the rest of this op at, because the 15 juggs will only come from 1 place, and that spot is exactly in front of u, when u sight in towards the fence gate. When u get really hurt, just lie down, facing the ladder, that way, u can kill the climbing juggs, then go back to the normal crouched position right after. This takes 20 minutes to do, due to the long times between each jugg, but l8r into the op, it'll change
Snatch & Grab - this level should be done in 2-player, due to all the times u will be downed. In this one, just take it extremely slow and steady, just wait till the music dies down to basically to a whisper before advancing, and always listen for the big gong before a jugg shows up to ensure ur 3 stars from this one. this one took me and my friend 25 minutes.
Big Brother - This 2-player mission gives u about 2 minutes extra, dunno why, but it gives u a lot of time just to get to the roof of Nate's Restraunt. The guy on the Vulcan turret will do about 96% of the killing, and the guy on the ground should only peek out and check to see if its ok. the only time the guy on the ground will really have to shoot is in the alley leading off the main road at the beginning after u advance down the road. This 1 takes about 15-25 minutes, depends on the person driving the heli. The recommended route for the ground guy is basically all the houses down the left side of the road, stay in between the houses, behind the occasional brick wall, and in garages, and once u reach the long stretch of empty pavement but a crashed heli and 2 civvi cars, just run to the blue car, wait a few seconds for the vulcan guy to kill a bunch of guys, then run to the black SUV, doing the same thing as with the blue car, then to the heli then run n gun to the roof, and make sure the vulcan guy kills the ppl on the roof before u get out of cover behind the heli, that way, the ground guy wont die going up the ladder outside leading to the roof.