The best way to boost this is with three people (this method also works very well for triple-boxing). Whoever’s going for kills can get around 8000xp in a 15 minute match, while the person reviving can get around 4000. I’d suggest at least getting the manuals for the starting two weapons of each class before boosting to rank 20.
An important thing to note is it’s best to marathon boost this or at least leave your Xbox on between sessions. The reason for this is if you exit out of the game completely any XP over 1500 you earned will be deducted from your total XP resulting in the loss of ranks and a lot of wasted time.
Create a ranked match on Last Bastion in Uprising and have the person going first on a team by themself. Near the center of the map is a grate with steam coming out, enter the door next to this and once through you’ll see a hole in the floor. You want to have all three boosters position themselves on the small piece of floor to your left between the wall and hole, making sure the team of two’s captain is in the middle.
Now just kill and revive. Press up on the D-pad to pull out your machete, hitting RT once with this is enough to down your opponent. You can attack as soon as the downed player starts to get back up, the reviver should just spam Y.
Remember you can call a vote to change the team captain from the pause screen. Once the vote has passed, kill the captain for the change to occur. This may be necessary to keep a rotation going so someone doesn’t end up reviving for two consecutive matches. After reaching rank 20 and unlocking all the weapon manuals, just do the de-rank glitch to reach rank 30.