I got only two Silkies and I am brand new at chickens ... so my expertise is limited. ;-)
I believe I have a boy (it's crowing) and a girl (I hope), so from what I've noticed:
The boy was always the shy one. We though it was a girl since the other Silkie had more of an in-your-face attitude, but it turned out to be the opposite.
He was always hairier then the other Silkie more feathered legs, more fluff on his head.
His ears are navy blue vs. aqua blue on the other Silkie, which I believe to be a girl.
The comb has always been slightly bigger/bumpier then on the girl.
He was my first rooster to start crowing! Thats why Im so confined he is a he! ;-) He started at about 2 months of age! He is one funny fellow. He could not make it any easier for me. ;-)