You start by allying Poland, Hungary and Castile, but not marrying them yet (marry them only after claiming Bohemias throne, don't marry Hungary at all)
Take the improve prestige mission
You marry Bohemia, after a few months Bohemia gets a king of your dynasty, claim their throne and go to war immediatly with the claim the throne cb. If you don't they get a podebrad king by event sometime in 1447. Finish that war by 1446/47, that gives you >50 prestige for 100 adm points
Now pick the Venice mission, call in Hungary with land promise. Give them Dalmatia, you take 2 provines, give Brescia to Milan (you don't need to, but it reduces the negative IA from provinces owned by non HRE members). If Byzantium still lives you can take Negroponte as well to get a claim and vassalize them (weakens Ottos for later)
Break Alliance with Hungary in 1450, so the truce will be up in 1455 when you get the Restoration of the Union cb
If you can get the first Pope war done before Hungary even better, don't take too much though
After Hungary you'll have massive AE in italy and southern germany and the only reason you don't have a coalition is because your diplomats have been busy improving with everybody and you used your diplo points to upgrade your gold mine to 10 production and your money from the gold mine to influence nations and gifts. Also have an improve relations advisor permanently
Now it's time to let AE tick down, you do this by going to war with burgundy to force the inheritance as that war costs no AE
After the war you wait out truces. Or, if you did not waste troops you can go to war with Denmark or Teutons with the imperial ban to acquire their imperial provinces. you need those later as a base for fighting the reformation
Later finish up Venice and the Pope, Force the Pope to release Avignon as well (you take everything else and therefore full annex him, when he gets released from the event all the negative modifiers have been wiped as he is a new nation, when he keeps Avignon and you give back Rome he'll hate you a lot making Excommunication likely)
Once you have time in between the wars you can also take the defend the netherlands mission, that gives autonomy reduction in all your lowlands provinces if you take rethel from france. Call in Castile and crush France (easy, it's you, Hungary, Bohemia, Castile, Aragon, Naples vs France and allies)
You should take Rethel and nothing else. If France does not rival you and Castile cancel his other rivals so he rivals both of you, that will allow Castile to get a Habsburg heir allowing you to PU them later
Use the rest of the warscore to feed Castile french land to gain favors (spend favors on trust, if you have 80 trust or more they won't cancel the alliance for stupid reason like you being the only rival)
Also while you have time conquer the balkans, it's a few provinces that are easy to get and add them for some IA
Disinherit often (unless your king is 5/5/5 and your heir 1/1/2), it's 10 IA for free. Especially your first king, he's 2 admin and 1 mil.
Select 2 electors (+Bohemia) that you improve relations to max so they vote for you
Don't improve with the others, there's a mission improving IA gain temporarily by making an elector like you that you only get if he doesn't like you in the first place (and more IA is always good)
Get diplo ideas first, religious second (then Influence, admin and humanist). You need diplo because of the AE and religious to kill the reformation
As soon as you got 4 diplomats (1 from diplo, 1 from imperial reform) always support your heir in poland, it's free monarch points and if you are king by 1600 they'll become a regular monarchy allowing you to PU them
With that strategy you'll be able to revoke by 1520-1560, after that watch any nation that got your dynasty (and is outside the hre). As soon as they got no heir break the alliance (if you have one) and immediately truce break them to force a PU. Castile gets your dynasty by event, Poland by supporting heir (with all your dip rep you'll always win). Also you might get lucky with additional nations (in my run England got a Habsburg as well), but those 2 are must have as Austria