Bunker snap looks is when u jerk ur head to one side then back again really quickly, the idea is when ur snap shooting u get a split second sight of the field which ur brain analyses when your in cover, protectin u from being shot. I do it all the time.
trigger walking practice is always a give away, on the mouse, on a pint glass, on the bus.
Gotta admit so far the ways to spot a paintballer have been fairly obvious :-/ "if hes wearing paintball clothing"
I also suppose that if he was running down the street, sprinting and sliding from car to car screaming CHECK HIM MARSHAL that might also be a give away....