Started in the Summer of 2012, "424" is a distinct sound that consists of only 4 finger positions, multiplied by 6 strings, yielding 24 notes (Hence why it's called "424"). The fret positions typically follow an XOXXOX pattern.
(Note: In this case, open strings represent the first X). Once you've got the four positions down, start combining them with different strumming & arpeggio patterns and experiment until it sounds the way you like it.
If you like the 424 technique, consider sharing it with other musicians to create new sound combinations; and perhaps submit your own version of the 424 sound in a video response; or just watch my progress of the technique, and maybe leave a comment, subscribe, share etc...