How exactly? (Please forgive the thread hijack)
General strategy for Austria is ally Poland, Castile and Hungary, marry Bohemia
Wait for habsburg in bohemia, claim throne and force PU
Declare on venice with Hungary, give them dalmatia, take 2 mainland provinces
break alliance with hungary in 1450, in 1455 you get either a PU or a restauration of the union cb
Anyway you should have PUed Hungary by 1460
Then declare on Burgundy and force the inheritance
From there it's Pope->Venice->Pope until you have the needed provinces for the shadow kingdom
Other tips:
Get provinces in north and east germany to get borders with as many princes as possible
decide on 3 electors that should vote for you and keep them happy (bohemia and 2 more, not saxony or brandenburg cause they often flip protestant)
don't improve relations with the rest of them, there's a +10% IA mission that you only get if your relations aren't high
Abdicate whenever you have a decent heir and enough votes to be reelected, it's 10 IA for free..also your starting king has 2 adm and 1 mil so get rid of him quickly
ideas should be first diplo -> second religious -> admin+influence as number 3 and 4 ->humanism fifth -> offensive ->exploration
As soon as you got 4 diplomats always support your heir in poland, it's free monarch points
Check who France rivals, they need to rival you and Castile so that Castile gets a habsburg heir via event. Often they only rival one of you , so you need to make them hate you both
Take the defend the netherlands mission, it gives you a claim on rethel and a monthly autonomy reduction in the netherlands making those provinces much more useful. declare war on France and call Castile into the war, this should be an easy war (it's Castile/Aragon/Naples and You/Hungary/Bohemia vs France and allies)
Take Rethel, remove 1 or 2 rivals of France and feed Castile land. France will then fill up his rivals after the war and both you and Castile now own french cores so the chance is really high of him rivaling you both - the event will fire pretty quickly (assuming you have a royal marriage with Castile and they have no heir)
I typically fight this war between 1490 and 1500, so before the Reformation. Next is killing the Reformation, Protestants often spawn in northern germany, england and scandinavia, Reformed in switzerland and scotland
Sometimes you can revoke before reformed spawns, then just diploannex the vassals that have Centers and convert manually (like you do if a nation is to big for force convert or the center isn't in the capital)
Around 1600 Poland will become a hereditary monarchy, if you did everything right they should have your dynasty (I had so much diplo rep, I had a 49% chance when supporting my heir). Force a PU on them, like you do on Spain as soon as they are heirless
After revoke you should always be at war, going east is the first priority, I was taking land from india in 1620 and ming in 1640. Spain will handle the new world for you, just subsidize their colonies and they'll do the work
