How are you handling the specialtisations for these skills?

I was hoping for rules in the new Winds of Magic, but none there were and it is continuing with guess ruling.

It seems that the same will be for the Signs of Faith, but I do hope there will be something at least.

Are you asking for special rules other than simply adding a fortune die or just what each specialty means? I assume you are looking for specifics about what each specialty means. Here's who I see them.

Channeling

Below capacity - applies when you are below equilibrium (Willpower rating).

Overchanneling - when you are already over your equilibrium or I guess you could make it when you are already at or above twice your Willpower.

Conservative or Reckless - when you are in the specialized stance

By college order - this one is a bit more tricky and I guess it could mean that you create a given circumstance in which your Order would benefit, such as an Amber or Jade Wizard using channeling while in a natural setting with abundant life. Perhaps for a Bright Wizard it would be while on the battelfield or near a bonfire.

Spellcraft

History of Magic - fairly self explanatory, more of lore check

Colleges of Magic - seems to apply to your Wizards particular College spells, so it would not apply to petty spells. Seems overly inclusionary since Wizards really only casts spells of their own College anyway.

Rank 1+ - applies to spells of that rank

Piety

Below capacity, Conservative, or Reckless - see Channeling

Urgent Need - seems entirely too vague and arbitrary as almost any use of a blessing could be describe by a player as urgent. Perhaps this could be turned into something like the Channeling specialty "by college order" so it would apply to a particular faucet of the faith. Like helping another for Shallya, or combat against enemies of the Empire for Sigmar.

Invocation

Each deity has its own specialization - This could be used just as I described in "Urgent Need"

Traditions, Rituals, or Tenets - I'm guessing this is why you said "mostly Invocation", these terms sound like throw-ins or hanger-ons, perhaps the designers had something in mind when they wrote up the Invocation skill, but it didn't make the cut. Perhaps there will be more rules for them in the Signs of Faith supplement, but your right probably not. I could see them being used in an official capacity, such as if the priest is using his blessings as part of some "traditional" use of his diety's power, but this would start intruding upon the previous specialization. Maybe the designers originally intended to give certain blessings descriptors like ritual and tradition. I chould see this since allowing preists to specialize in blessings by rank doesn't seem to fit the flavor of the setting like it does for wizard spell ranks. Hopefully someone else will have some better ideas on this.

Hope I helped.

i won't agree on the Spellcraft specialisation : College. There is already specs to cast spells (Rank 1, 2, etc.). A fixed permanent bonus on all spells (but Basic) doesn't go in the right direction to me. It feels more like a knowledge spec about your own order (people, sub-groups, hierarchy, history and traditions, special rules, etc. of your own College).

And to be on par with Priest, i'd use the same for Invocation (and Piety would also work as Channeling)

"It feels more like a knowledge spec about your own order..."

Good point!