Completed this with 4 people
Our Classes: 3 people with medic and 1 with engineer
2 with IMS and the other 2 people with vultures.
Boosters: 1 person with Armour, 1 with feral instincts, 1 with Team Boosters and 1 with explosives(can swap it out for something else like another Armour). Everyone with Explosive ammo. Also put on Shield to protect your back. Allow everyone to have atleast one good attachment like grip,muzzle brake or rapid fire.
Everyone spend their first 4 points on the boosters and the person with explosives upgrades Ammo instead of their booster. After get one person to upgrade medic or more can do it its up to you. Grab a LSAT to defeat the breeder in under 90secs if you get that challenge. Also upgrade your pistol so you can have 2 primarys, so you can get another primary for the challenge. Put Feral Instincts down if you get the leper challenge. To easily spot it out it is the one with the bright red face when instincts is active.
Why Engineer? When engineer is upgraded they can have upto $8000 in their wallet making it easier for you to do the money challenge and they get more trap and explosive damage. It also helps you repair the drill easier incase you get the challenge to not let the drill health drop below 50%. They can also drop money for other players when their wallet is full by holding down 'LT' and 'A' at the same time for a few seconds.