Video Instruction:

https://youtu.be/heTURyy-TD8

Text instruction:

The best way for fast leveling, is too kill a lot of low tier units such as grots or sluggas, cause its pretty easy and
they dont pose danger to you. For that case - firsts arenas are best choices. But y can do it even in more efficent way, with one trick.

Point overtime bug

To do it, y must have at least 2 players in game. When timer reach 0:00 and y still capping point, its going overtime mode (as long as you in point cap zone, y can cap it, but when y leave - y lose immediately). To bug it, y must die in a point, when overtime mode is started. You other ally must be somewhere else( not in a point zone with you), cause your body is keep holding overtime. When y respawn, y can start farm infinity waves of coming orks( cause this is how point waves work, y cap it before get overerrun). But remember, not going in point cap range( cause y lose it when y run away, or y must cap it, or die in it again).

You can do it in any arenas with point wave. But in my opinion, first calkys with 2 point cap at the end(like in video), is the best, cause spawn only sluggas and rokkets. Shootas are pretty dangerous when in mass blobs, cause they shoot with tau aim at y, and never miss.

You can farm it with 2,3 or 4 players. Even solo, if someone help start overtime bug and leave y.

Remember only 26.6% of your score are going in to your exp. And yr max score is 99999, so after y reach it, y can die and press NO on continue screen, cause if y restart arena, y dont get yr exp.

here some information about how much y need to get another lvl:
https://spacemarine.fandom.com/wiki/XP

With max score 99999 y can get 26324 exp and no more.