After interaction with the mask you will get 1000 points, so it's the easiest way to earn them.
Points amount doesn't scale with game difficulty, so you can just start games on easy with frequent helicopter probability over and over again

You can find the mask near Slaughter House on the mountain


Here are screenshots from the video, in case you have playback issues

You can also use the Hardcore Survivor perk to get double points from the mask