I don't see any difference in rooting depth whether you plant them or broadcast them.  The key is planting date, any time in the summer, Sept 1 is about it to maximize benefit here, too many plant a little too late and will get benefit but not what you would get earlier.

The corn planter does as good a job as anything, really scatters that little seed out sparsely so benefit is maximized to cost.

15 inch rows are better than 30 to me but they both work.  Drill works great for seed to soil contact but you use more seed.

The main idea is just plant them!  If you haven't tried, them, try them!

Ed Winkle