Hemp grown for the seeds or grain will be harvested when ~70% of the seeds are mature. Grain heads are going to be relatively wet, so once combined, seeds will need to be cleaned and put on aeration within 6 hours of harvest. Growers are using traditional combines with draper headers with the most success.
Seed cleaners are being used to remove green material, immature seeds, and weed seeds. There are cleaners designed specifically for hemp seeds.
Processing after the seeds have been dried will depend on the desired end product. Cold press machines are used to crush the seeds and get the fatty acid-rich hemp seed oil. This oil is added to food products or cosmetics. Hemp hearts are dehulled seeds. The dehulling process required cracking the hulls and removing them.
Hemp as animal feed is not legal for commercial livestock operations, however, there are ongoing studies addressing this issue. Hemp Feed Coalition