The galley strat is the best i believe, and is also what i used. Lowered maintenances, sent diplomats to Poland and Austria and just waited. When i had about 27-28 galleys Ottomans declared on Candar and i declared on them alone.
The trick seems to be not waiting too much. I was allied to Austria, Poland and Aragon(which was also allies of Venice so they kept them at bay) when i declared. None of them joined

But if you can catch a small piece of Ottoman fleet on the day you declare war, the rest becomes no problem. If i remember correctly i had about 34-38% war score, took back my cores except Edirne and got 2 Bulgarian places to connect Constantinople.
After the first war the challange is basically over, though for following wars i wish i'd released minor Anatolian nations before fully taking European parts, it'd lower Ottoman force limit for easier land battles.
As a note, i took humanism+religious and it is insane! So much tolerance of own faith:happy: