Millet is easy to seed, as it is a small seed and we used to just blow it onto the field with a Valmar spreader and then harrow the field. We could seed and harrow a 100 acre field in a few hours. We have also used an old steel wheeled drill that sat in a fence corner here for decades. We pulled it out, oiled the chains and cleaned out the seed box and it worked great. I'm pretty sure you could seed it in a variety of different ways. It should be seeded shallow and don't stand too long in one spot or it will grow up inside your pant legs!!
Another choice may be sorghum- sudangrass. We have seeded it as late as July 20th after a rain and got a good cut of feed. It is sweet and the cows go crazy for it. I have also seeded it and let the cows graze it in the fall. It is best if you can get it off the field before a frost because it goes pretty flat once it is frozen. In the 80s and 90s we sold sorghum- sudangrass seed and my parents won trips to Florida and to Cancun for top sales in Western Canada. We have not had severe drought like that since then so we have not seeded it since. In 1988 our sorghum -sudangrass was 6 inches high on July 1st. We had a good rain on July 6th and a few showers after that, and it was 5-6 foot when we cut it in late August. My dad put a large stake in the ground and marked it in inches, and it was growing at 3 inches a day. One hot day after a shower it actually grew over 4 inches in a single day. The thing about sorghum sudangrass I liked was if it got dry, it would go dormant and it looked like it was almost dead. When it rained it immediately started to grow again. It is not very high energy but has decent protien and it is a lot better feed than snowballs and northwest wind.