how does he do it?

exhibit A – as you can clearly see from the picture above
shane barnard strums way too fast, i swear this photo is not photoshoped!!
a few of my thoughts:
- (1) a thinner pick is easier, try 0.50mm to 0.60mm
- (2) its mostly in the wrist… try to keep it loosy goosy
- (3) loosen the grip ever so slightly on the pick
- (4) the double turbo strum is controlled chaos. without rythym it is just chaos
- (5) practice with some basic repetitive chords, speed up as you get more comfortable
- (6) make sure you dont loose the rythym!
- (7) dont double strum while leading worship unless you are really really really good at it
a few thoughts from others:
it can sound terrible if your wrist cannot control the pick. trust
me…you will think its cool, but its terrible until you can strum
correctly. also, i would suggest trying to “shane strum” quietly. if
you can do it quietly, without letting your grandma hear it across the
house, you MIGHT have it. this is really an advanced technique. it
shouldnt be done until you can do it right. practice scales and
arpeggios first…those are more important than double strumming. 
-Paul
As far as the quad strumming thing
goes, that is just learning to play REALLY FAST in time. Practice
playing an easy punk tune and switch from single strumming (the typical
down, down, up, up down up) to double strumming. It’s more about the
thought process behind it than the actual mechanics of doing it. Many
people are able to physically make their hand move that fast, but they
can’t think it IN TIME.
-Tim
Musically, I grew. Just imagine
strumming the guitar every day with the prodigious Shane Barnard. I
quickly acquired his infamous double strum, which incidentally is now
quite annoying when random people are banging away with the double and
triple strums trying to emulate Shane. But more than music, I learned
about selflessness from Shane. His desire to do what pleases the Lord
was a constant abrasion to me, in the sense that the more time I spent
around him, the less selfish I became. I would hope to think that it
was an iron sharpening iron situation, but I easily learned more from
him than the reverse.
-Caleb Carruth
Its all in the hips…its all in the hips….d’oh! I mean…wrist…its
all in the wrist. Oddly enough it really is an aligning of the brain
and your physical capabilities (same as in lead guitar playing). There
are times when i feel and think i can pull a deca-strum…but my wrist
would shatter. Rhythm…is a funny thing. Its something you cant really teach
somebody, you either got it or you dont. Think outside the box. Break away from
full constant up down up down strums. Do whatever…i dont care!..as
long as its in time and rhythm. Dont be scared to try something.
There is so much stagnation in music…just try something, anything!
-Jeff
when i first tried the double strum, i
wanted to burn my guitar and just stick with the moraccas, but then i prayed
about it and aked for the Lord’s help, and then after a few weeks i finally
got it down perfectly. i found that if you hold the pick so that one of the
rounder corners (not the pointier one) hits the strings, it makes it 50%
easier to double strum. and just think of double strumming as “kicking up”
from a down-strum half way down and then strumming normally again,
continuing the rythm. and note: holding the pick harder does not make your
wrist move faster, keep the pick firm, but not too firm, and loose, but not
too loose. i hope this helps somewhat.
-tom h.