Very little of our hunting is on public land, although there are some good spots (Merrymeeting Bay, Brownfield Bog, Scarborough Marsh, to name a few) that have a lot of public land.
However, state law gives you the right to access any "great pond" (basically anything over 1o acres) or the intertidal zone to "fish or fowl". (It's more complicated than that, but basically if you are in a boat or below the high tide line, you can hunt just about anywhere so long as its 100 yards from the nearest building.
There is also an awful lot of private land that is not posted. Needless to say, it pays to get to know the landowner of spots you plan to hunt. I've only ever been turned down once when I asked permission.
As for the blinds--there are some, and legally they are first come/first serve if on public land, and belong to the owner if on private. I generally don't hunt out of someone else's blind, although I have on occasion on public land. Maine has a lot of trees and brush, and it's generally more productive to find a natural "blind" anyway.