I suggest you start with a cross of black sumatra and black silkie. That can give you black feathers, black skin, crest, feathered feet, and long tail. The crest, feathered feet, and long tail are dominant genes: you should see them in the first generation of chicks, although those traits won't breed true until you've done several generations of selecting.
Silkie feathers are caused by a single gene, and it's recessive. So you won't see silkie feathers in the first generation crossed chicks, although a few may pop up here and there in the future.
Silkie crosses will usually have a 5th toe and muffs/beard too, so those are traits you'll have to breed out; but each is caused by a single gene which makes it easier, and they're both dominant--so when they're gone, they stay gone, unless you cross to the silkie and bring them back again.
It looks like your idea of "cochin body type" has more to do with the loose, fluffy feathers than the underlying body shape. Sumatras have hard, close feathers--but you might get looser feathers when you cross to a silkie. Otherwise, you might have to cross a cochin in at some point.
If you can find a silkie that lays blue eggs, you won't have to cross in anything else. Just cross the "best" chicks to each other or to one of the parent breeds as needed. (Yes, some folks do have silkies that lay blue eggs.)
Otherwise, cross to an Easter Egger or Ameraucana at some point to get the blue eggs.
You could start here:
http://www.edelras.nl/chickengenetics/
That page links to several others, and is a fairly good starting point for learning chicken genetics.
