I have new construction lawns where customers wait 2 to 3 months before putting in a new lawn. In that time the dirt has been taken over by weeds. We do hydroseeding, so we want a weed free and dirt lawn before we spray. I was thinking mowing the weeds down really low, collecting the clippings and then using a pull behind counter rotating tiller to kill the weeds which will prepare the soil bed. Or would it be better to use Round up, mow the weeds down collect them, and then till? My understanding is that tilling kills the weeds immediately, so if that is the case I could save myself an extra step by not doing the round up. Please give me the best advice!