Well as far as grasses go, I thought you just let 'em do their thing and they will seed themselves.
My imaginary process so far, goes something like this; 1) sow a bunch of seeds, 2) a week or so after germination harvest the 'lawn', 3) let the grass regrow and flower, 4) collect the seed, 5) completely harvest the grass (roots as well), 6) repeat steps 1-5.
The only problems are, getting the seeds to germinate at the same time, and recovering the seeds from the flowers. Not to mention the possibility of cross pollination from other grasses.