First put up the feeder and see if you get them. They will have to learn to find your new feeder.

100% cotton balls are ok... I fluff them up some. But what I have been using now, are the stuffing from my supplements. Not all vitamins come with cotton stuffing anymore, but many do.

Birds do strange things... up north we had a wind sock made of mylar with mylar strings at the end to dangle and catch the light. We used to find those woven into nests years later!
People upNorth use them on docks to scare away gulls from sitting on the docks and messing them up. So it was interesting to see these broken off strings end up in nests. Obviously those birds liked the "glitter" effects! They were about 3/16inch wide.

The finches don't lay their eggs until later in the season.
http://www.birdfeeders.com/advice/bi...dfinch/nesting
http://www.wild-bird-watching.com/Am....hJ7Iio7U.dpbs

We've never had much success with Niger seed. We give shelled sunflower bits, that we buy in small bags. I have my nesting dispenser in the backyard, and the feeder in the front of the house in the kitchen window. The nesting dispenser is in a mock orange bush hanging from a stout sturdy branch. The leaves from above make the birds feel protected from predatory birds etc.

The first year I put the cotton out it was for the hummingbirds. But it didn't get taken. Last year the finches showed up...and this spring I have both finches and chickadees. I still haven't seen a hummer take the cotton! So the finches didn't come right away. You can also stuff cotton in the notches of small bushes. That way the birds get used to the idea. We used to do this with our cat hair (from brushing), and it was always taken, but we never saw who took it.