I have a 1/2 acre area that is already close to what I want, but it's infested with both tall and creeping buttercup. I say "close to what I want" because it is also filled with rushes that I would like to keep (mostly common rush, Juncus effusus, but also a couple other varieties). I would like to get rid of most of the buttercup so that I can plant grasses and some wildflowers. I don't expect to eradicate the buttercup, but I want to reduce it enough to give the grasses a chance to get going. I'm wondering what the best approach is.

I would be willing to do an initial broadleaf herbicide application, but I can't seem to find information about whether something is available that would not harm the rushes. Is there something? Another option is to attempt to apply glyphosate (sponge, saturated glove, spray with shield). Of course, there is mechanical removal, but this is a half acre, and it's just me...and I would like to try for planting grasses this fall.

Ideas?