theres no hard and fast rule to stumming how many strings for that sound. As someone mentioned, the sound of that does sound seem like striking the strings before the guitar nut.
So basically, you should be striking the strings at the space between the tuner and guitar nut.
Theres wont be any pitch involved here, just plenty of volume, even with no distortion, that sound can be achieved. Of coz with distortion, there will be another variation of the sound.
As for whether is it up or downstroke, the usual way is to go downstroke, hitting the thickest string first then the thinnest. The reason is that you wanna get the strongest "pinging resonance" when your geetar pick strike the high E(thinnest string) last and let that sound be amplified out from the amp
anyway, theres a live video of the same band with the geetarer doing the same thing and much clearer looking. Its a live video of some afternoon festival which they are playing revenge of the surf queen/super nova. That particular sound was done again in the song supernova at around 3.34 sec with the cam focus at the geetarer.