I see posts asking for people to join boosting lobbies. But, they require you to have prior knowledge of KoTH boosting.

What you need:
Any DLC (So you can play in social matches)
2 Controllers (Not needed, but is easier to find a boosting group)
Time and Patience (Long matches)

Process:
You have 2 groups of 5.
One group searches for social KoTH
Once in a match, the other 5 need to join session, to replace bots.
Once all 10 people are in you should folow these steps.

Both teams meet at the hill.
Everyone in one team stands in the hill to capture it.
As soon as you get your +200, the other group needs to step in, contest, then step out.
They repeat this process until you get 119.
Then you do the same thing. They stand in the hill, once it's captured, you contest, then step out.
Let one team win (120) Next round, repeat everything again, but let the other team win.
Then just decide on a winner for the last match.

Why social?
Social can put you in groups with bots, allowing you to join session with friends, ect..
The best thing about social is it keeps the same lobby, meaning once all 10 are in, they are in for good. The maps just cycle alphabetically.

Math stuff.
KoTH gives you 50% (1/2) of your score as xp.
+200score (100xp) for each capture.
+50Score (25xp) for each contest
100xp * 119 caps = 11,900xp
25xp * 119 = 2,975xp
14,8750xp * 3 rounds = 44,625xp
(September 2-5 [15x XP])
44,625xp * 15x xp = 669,375xp.

So everyone in the game will get ATLEAST 669.3K xp per GAME.
The team that wins 2 rounds will get a little bit more.
And I did not factor in killing, because organized KoTH boosting, you don't kill. (But it does happen)

Any questions? Please ask.