A couple of things: 1. I have tried hand seeding it with a bag seeder and I have had it drilled in. Try as I might to get the seeding density right, every time I have hand seeded it I end up with it too heavy. That leads to stunted growth AND thinner stalks, which will go down sooner than good, normal diameter stalks. It is still of benefit to the wildlife, but not so great of a screen in this case. When I have had it drilled in it has been perfect in terms of density and those stands grow taller, stand longer and screen more.
I think 10'-12' would be a sufficient width for a screen...with this caveat. The last two years have been drought city in my area, so the EW is thinner than I am pretty sure it would have been had we received ANY rain on it. EW, milo and sunflowers are in my experience the best drought crop options there are, but I am sure we would all agree that even a drought resistant plant would do better with some rain.
Bottom line...drill baby, drill.
But you can grow it via broadcasting and light tillage/cultipacking.
2. I would say on a scale of 1-10, with 10 being you can't see through it from 5 feet away, that EW would go about like this month to month. August-September = 10. THICK stuff!! October = 9, November = 7, December = 5, January = 2-3, February = 0-1. Now that is my experience and again we have been battling dry summers for at least the last three years, with the last two being essentially NO rain in the summer. Even with the lack of moisture, the stuff is still 10' tall. SO...might those numbers be better if the plants got even
some rain while they were growing? I suspect so, but I can't say from experience either.
3. Think of corn or milo though if you do plant it, as EW thrives on N like the others. Unfertilized EW will grow some, but well fertilized EW will about double the unfertilized.