Harold, that's what I've been doing the last couple years. I spray wait about 3 weeks. The grass falls over on its own. Then I sew my seed into it. It stays fluffy, not matted down. The seed sprouts under it, but has to be several inches high to even be seen, so it protects the young sprouts to let the field get established. Eventually, the thatch will decay and lay completely down and start feeding the soil.