I live a long way from Maine, but I've photographed the coast a few times and will do so again this fall. Here's a few thoughts, beyond the general advice to stay as close to the water as you can.

From your base for Schoodic, visit the harbour off Corea early or late in the day, maybe both

Don't ignore the downeast coast. From Schoodic you can drive to Lubec and back in the day with plenty of time for scenic detours to places like the West Quoddy Light. Its less manicured and touristy as you get east of Acadia

I'm not a fan of the Acadia NP, but dawn or sunset from the top of Cadillac mountain is photogenic-not as photogenic as it will when I'm there with leaves on the ground cover having turned to red- but nevertheless good.

I do like the peninsula to the west of Acadia NP, which leads down to Stonington. Castine is good too.

The peninsulas just south of Boothbay harbour offer scope for decent photography. Allow plenty of time when travelling along other nearby peninsulas suchas Pemaquid- they always seem to take longer than i think.

There's a few examples on my site at www.photography001.com - look in the "By the Sea" and "structures" portfolios.