the xxxxxx thing is very often used in reaggea, ska and such beat-based music. When you get it sound well, it's very fun to use..
And, it's usefull also on none-electic guitars. Use wider movements with your pick-hand (your right hand if you use a right-handed guitar), that makes it easier. When you got it, try to play a chord, then play it again, now only thouching the strings slightly with as many fingers as you want (more than one, otherwise you may create natural harmonics), to mark the beat, then play the chord normally again 2 times, than mute them again. Repeat this and if you got it, it will sounds pretty good. Also get yourself a drummer who can play backwards, makes it even more fun!
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