If you would like to get this done in 2 hours of boosting then follow what I did.
First you want to create a 12 man session. Set it a week in advance to give your boosters time to join. It will help if people can double box but it's not necessary. Also if you're short a few players, no worries. You can vote to kick out any randoms who join.
First you want to organize the parties since you cannot have more than 8 in 1 Xbox 360 party. We had a full 360 party of 8 and then 4 others in the Xbox One party. I was in both as I was the session leader and needed to switch back and fourth between the two parties to make sure everyone got it.
Once the 2 parties are up, start by forming two game lobbies of teams of 6. You decide who is on what team but to make things simpler, I invited the first 6 people to join my session onto my team while the 7th person to join the session invited the rest. Once both game lobbies were put together, I searched with my group first on Treasure Hunt. (NOT TEAM TREASURE HUNT). Once we got into a lobby, I checked to see if there were any randoms. Kick any that may be there. (Press Start then RB over their name to vote to kick, then everyone press Start to accept the vote). Once we were in a lobby by ourselves, I told the 2nd party leader it was okay to search. He searched and we got matched up almost instantly. 12 players locks down a lobby so you won't have to worry about randoms. Kick any randoms who may join though.
Once that is all set up, vote to skip the map until you get Oasis. Do this every time as Oasis is the boosting map to go to. Once you get into the game let everyone know what's going on. Tell them don't shoot and run to the trap in the back corner up the stairs. Don't move, just start jumping once you're there. Once everyone knew where they needed to go, the person going for the trap kills sits back and shoots the yellow symbol up top which activates the fire trap. It is important that they do not pick up any trophies as it will end the game faster.
Once everyone dies, just keep running to the trap and getting killed. Be careful not to pick up too many trophies. You guys want to even it out a little on who is picking up trophies. 8,000 points is what it takes to end the game and whoever is going for kills should be the one with 8,000 at the end. Once the player is at 7,000+ points it means the game is nearly over. So they should wait until all 11 boosters return to the trap to die. Once they're all there, kill them with the trap for the max amount of kills. I don't know if it was a coincidence or not but 54 kills seemed to appear quite often for almost everyone so 2 games for every person. Once you get the achievement, go into the pile of people and the next person goes.
When deciding who should go next and whose turn it should be, always use the session order of how they joined. So you should go first, then whoever joined the session second goes second and so on. Also if you are the leader it is your job to switch between the two parties to talk with people and make sure they understand what is going on.
This worked out perfectly for us and I hope that it does for you too. Any questions before setting up a session, feel free to ask. It took us less than 2 hours to get everybody done.
If you chose to do this with just one other person it will take a little longer though you may run into randoms and sometimes you can't vote to kick them if there's too many. I preferred 12 as we didn't have to deal with the randoms but it's up to you.