This is very easily done by running through the missions on easy. Remember to activate "Competitive Time" in the mission select menu.
Tayari Plaza: 3 minutes
- Very simple. You can run past all the enemies in this one. Should be no trouble at all.
Uplift Reserve - 4 minutes
- Get in the Warthog as soon as possible and drive past all the enemies. Swap it for a ghost as soon as you find one.
Kizingo Boulevard - 9 minutes
- Get in the tank straight away and obliterate the two wraiths, then proceed through the mission destroying everything with the tank. This should present no problem. What may slow you down is the end where you need to hold your position with Dutch. When the phantom holding the wraith drops it, board it as soon as it drops and destroy it. I'd advise to have a plasma pistol/SMG combo for this entire section.
ONI Alpha Site - 13 minutes
- As soon as you start, run and arm the charges, then head straight up the ladder to be ready to activate the switch. After this, run down and be ready for the next door to open. When in the courtyard, take down the hunters first, then obliterate all the others. Once again I advise a plasma pistol/SMG combo. Run up to the ridge and wait till you're ordered to retreat into the building. Once inside, swap your SMG for the shotgun one of the policemen is holding, then get on the turret and annihilate the enemies. You may need to get off the turret and kill any hiding enemies to proceed. After, kill the enemies coming from behind you and be ready to get on the elevator with Mickey. Once you reach the top, just use the plasma pistol combo to get rid of the brutes/jackals.
NMPD HQ - 10 minutes
- You can run past all the enemies up until the very end when you need to hold your position with your squad mates. I'd advise you to get a plasma pistol earlier on, and pick up an assault rifle when you get to the end part. During the end part you'll need to swap between the two mounted missile pods in order to dispatch the banshees/phantoms quickly, but make sure you don't detach these pods. Remember to use the plasma pistol/AR combo to kill the ground enemies.
Kikowani Station - 10 minutes
- This one shouldn't cause too much of an issue. As soon as you start, kill all the enemies quickly (pick up plasma pistol) and get in the banshee and be ready to proceed to the next area. During the areas where you need to manually open the doors, make sure you're out of the banshee and ready to open them quickly. Also be careful of the anti-air wraiths. They shouldn't be a problem on easy, but you never know. When you get to the Scarab, the door to the left of it can be opened manually and you can proceed without killing the Scarab. Remember when you reach the end with all the explosives on the wall, you need to destroy them to finish the level.
Data Hive - 16 minutes
- Pretty easy one. You can run past most of the enemies. Keep an SMG at hand and pick up a plasma pistol or a mauler whenever possible. When you reach the superintendent, be careful of the brute with the hammer. Make sure you focus on him and force him to activate his invincibility. When this deactivates, finish him, then pick up the hammer. You'll need it shortly. After you come back out of the superintendent, destroy all the dropping troops with the hammer. You should get a load of multi kills.
Coastal Highway - 25 minutes
- This is a long one, but shouldn't be too difficult. When you start, pick up the shotgun from the cache as you exit the building. This first section should be very easy. Go up the lift yourself and melee the grunts on the turrets, then slay the rest with the shotty. During the highway, make sure you swap vehicles if your current one is damaged, or you find a more powerful one (Gauss/Scorpion) When you get to the drone part, get out of the warthog and shoot them yourself. Buck is kinda slow at shooting them. The end part is a bit long, but shouldn't be too hard. You should try and get there by the 15-17 minute mark to give yourself plenty of time for this part. Remember that there's weapons, ammo and health in the building where the Engineer is taking shelter. There's also a turret and sniper rifle on the top level. If you have rockets, you could try and kill a group of enemies as they are dropping from a phantom to save time and ammo, but don't stand too close. Watch out for the hammer brute again.