Best/fasted way to level up

I know there have been a lot of threads and post/videos on leveling up in reach but i’ve heard the best legitimate way it to do gruntapocalypse, firefight arcade and firefight doubles. The doubles and arcade in particular as they get 4000-6000 points every run compared to gruntapocalypse where you get 1000-2000. Can anyone confirm this?
Thanks.

Team of four grifball is how I used to do it. 6-15k a game. If you run swat 4s it can also go really quickly.