i don't pretend to be a master at this, but here's my take:
transcribe! anything you can hear those guys playing, you could potentially play - just figure out what they're playing and how it fits in - or how it doesn't fit. transcribe and analyze - make sure you know how each note fits in harmonically and rhythmically.
make sure you know all your scales - the 7 modes of major, melodic minor and its modes (some of those modes are used almost never), harmonic minor (and modes, if you're ambitious), whole tone, and especially DIMINISHED! i hear so many guys using diminished scales and patterns to play over dominant chords (such as gilad's triad lick at 4:13 on this video:
a lot of these guys - especially kurt - practice these scales using patterns - which is a good way to learn the scales and get a lot of vocab. pick a pattern, like 1-3-5, 1-3-5-7, 1-2-3-5, 1-3-2-4, etc. (or any pattern you hear someone using) and learn how to play it fluently through any scale, any mode. and do it backwards, any way you can think of.
there's a lot more advanced techniques that i don't know about, such as maybe playing over a chord with pentatonics from different keys, so you get different sounds, but my advice is just to take whatever you hear that you want to be able to play and learn how to use it..just gradually start building a vocabulary from those guys and eventually you'll have to end up sounding like them..that's my goal, at least..if you take your favorite licks from everything you hear, eventually you'll sound exactly how you want to sound.
for chord voicings, if you're interested, check out vic juris' book on modern chords - covers a lot of different chords in a small book. covers triads, stacked polychords, and mostly different structures you can use for comping. i hear a lot of guys using those structures - gilad, lage lund, mike stern, vic juris (of course) probably kurt and ben monder. also, any chord you hear one of those guys you like playing, just transcribe it an analyze it, and then you'll know it!