I'm thinking it may be a fool's errand for an early attack given Austria's immediate disadvantages. Greater Germany as Austria is easy, but only in the long haul. NGF can only be formed by North German primary culture. Even with few army tactics the first war can be easily win. And since at this time, Prussia is in revolution, some rebels should pop more often, watch Berlin and the polish cores (with most of prussian soldiers by the way). You might need lots of Cavs (+2 recon), even in the first war. The second war should be add to sphere, but it might be very quick : if Prussia has enough time to recruit regular troops, it would became a great power again, so no sphererling. If Prussia didn't mobilize, provoque it by mobilizing yourself and obviously dismobilize ASAP ( like 3 days after !).

Let the AI try occupy some of your forests and hills with 25k+ men deep in your territory, circle, and nuke.

Occupy 100% of Prussia (and add additional troops in the places your ally occupied first in case of white peace), wait(a lot), and accept peace offer when the humiliate CB would make Prussia's prestige down to zero. Ally and attack with any european country with more than 5 ships.