If you haven't noticed, riot shield boosting is an efficient way to gain xp in boosting. Giving up to 125K XP to BOTH players in one game if both are using one man army.
First off, to riot shield boost you need:

12 Players
Organization
One Man Army(Pro if possible)
P90 AKIMBO / LMG ( AKIMBO P90 can empty both clips in five seconds compared to the LMG speed of 10 seconds to empty a clip)

When you are boosting in riot shield, one will start off with the P90 Akimbo(if you don't have P90 Akimbo, just use an LMG) and the other with a riot shield. The one with the P90/LMG will shoot the shield until the entire clip is gone for both guns. After this, both will use One Man Army and switch to either P90/LMG or Riot shield. Then the other will do the same. Just keep doing this until the round is over. And that's basically how you riot shield boost and gain 100K+ xp for BOTH players in one game.

1. Start up a lobby
2. Get 12 people
3. Invite 6 people into a party
4. Search for a match
5. Invite the people in the party
6. Find your partner
7. Private chat your partner
8. Find a meeting point
9. one will shoot into the riot shield with a p90/lmg
10. Both will use one man army to switch to the opposing class
11. Whoever has the bomb, plant it when there's only 10 seconds left.
12. Do this every round for 7 rounds.

EDIT: NEW WAY FOR PEOPLE BELOW RANK 45
If you and your partner are both under 45, try to both get G18 akimbo.
Once you do, use scavenger pro. BOTH will be riot shield with G18 akimbo
Meet up, shoot the shield, switch to the other, shoot, wait 10 seconds and repeat.
This racked me 100K points and my partner 95K points
However, this is not as good if you have p90 akimbo and one man army.

Note that this will own your accuracy and make it below 10% [ Register or Signin to view external links. ]