(adsbygoogle = window.adsbygoogle || []).push({}); Using bonuses, you can get 300-500 (Approx.) per kill depending on rank because of the perks needed.
This is the method me and my friend use.

Buzzkill Execution Method;
Main Weapon - Whatever you want headshot with,
Secondary - Anything as it won't be needed,
Equipment - Tactical Insertion,
Perk 1 - Any will do
Perk 2 - Hardline
Perk 3 - Last Stand
Killstreaks - UAV and any other two.

1. Meet up with your mate.
2. Player 2 (P2) put down their Tact.
3. Player 1 (P1) shoot P2 in the leg a few times until they are in LS.
4. P1 line up and Headshot P2, You'll get 200 for headshot kill, 100 for First Kill and 100 for Execution.

(This is where Hardline comes in)
P1 now is classified as "Buzzkill-able".

5. As soon as P1 gets their headshot, they place down their Tact.
6. Like before except this time P2 shoots P1 in the leg until they're in Last Stand.
7. Line up and headshot P1, You'll get 200 for the headshot, 100 for Buzzkill and 100 for Execution.

P2 Is now classified as Buzzkill-able

8. Repeat this until a player has won, then reverse the first headshot order so that the other player wins next match.

At first, it might take a bit longer than normal but once you get use to it, it will take about 4 minutes. So if you were to win you'd get about 400 x 20 + bonus = around 9 - 10k EXP overall for that match, even more with challenges!

I will try this with my mate also.