Chickens , rabbits, and seed balls

My partner and I are planning on running chickens through pasture to follow up with spreading seed balls. There will be plenty of green mulch available too. A few questions:

1. which breeds would people recommend for tearing up fallow pasture of grasses, goldenrod, yarrow, and queen anne's lace?
2. how efficient will three or four flocks of 15-25 chickens clear a 10' by 30' patch before moving on?
3. would moving rabbits through first offer any advantages or are they picky eaters? breed recommendations?
4. will we definitely need to run the chickens over a space more than once? will seed balls hold up against the birds provided there haven't been sufficient rains for germination? is secondary clean-up a good job for rabbits?

5. what are we not taking into consideration?

thanks in advance for your time!

frank