I accidentally put roundup on the entire lawn although it was only half the recommended concentration so some grass is pretty much all dead and some is dying, some in the shade looks pretty much fine. I was thinking about hydroseeding, or is that overkill. There is still some green pieces of grass underneath but for the most part it's dead. Or can we just spread seed over the top after mowing really short or do we need to thatch first and get all the dead out?