Fast triadic strumming on the treble strings (with a thicker pick)

[Zero G]

Do any of you play any fills or pieces involving fast triadic strumming on the treble strings with a fairly thick and/or firm pick? I was at a Guthrie Govan clinic, and Guthrie played my guitar briefly. He did this type of strumming ascending linearly up the neck, and I couldn't believe he was doing it with a really stiff Red Bear pick. What do you have to do to be able to strum like that? I can tremolo pick on one string really fast, but when I add in 2 or 3 strings my pick always gets 'caught up' in the strings...