If sees little no light....don't expect much if anything. I'd be focused on removing N/S running rows of Spruces to create lanes that will receive optimal light given your situation. If not an option treat it like a sanctuary/bedding option, especially for thermal reasons in late season.
How deep is the needle bed under the trees? the soil is going to need to be treated under those trees for anything to grow.
I had a very mature row of spruce trees in my backyard when I bought my house. It was pretty much bare dirt under them, nothing grew even with the trees limbed up. I cut them all down and did nothing else and now it is some of the thickest grass in my yard. I'd go through and select cut patches and rake all the needles out of those areas and you will be surprised on what grows up. Make sure you leave plenty of trees for good cover also and you can create a perfect bedding area with food within.
