By one person, enough to feed many people? I believe I have, at least for wheat and hulless oats/barley.
I thought of this from thinking about clay balls, and also from looking at the way wild rice grows in nature.
I think the trick is to get the plants to grow in clusters, sort of like the rows and columns you see in machine-planted industrial agriculture fields, but with several plants per spot, and more space in-between.
To achieve this I propose using seed balls, not in the normal way seed balls have previously been used for grain, with one seed per small ball, but more like seed "bombs" with several seeds per large ball. Dropping them in place would most likely be preferable to throwing them for this purpose.
Experimentation will be needed to determine the optimal number of seeds per ball and distance between clusters. Also whether a living mulch like clover would need to be used or if the spreading roots would do a good enough job of suppressing weeds on their own.
Most of the pain and effort I see when I watch people harvest grain by hand is in the cutting the stalks and getting the plants to lie straight on the ground, either on your hands and knees with a sickle, or with a scythe with those very cumbersome and inconvenient-looking finger attachments. And also in the tying of the plants in bundles, usually an entire second job for a second person.
Growing the plants in clusters would eliminate both of these things. All you would have to do would be to grab the cluster of plants beneath the seed heads and cut it below that. No specialized tools needed, a cheap sickle or even a machete would work. And thus it is already in a bundle in your hand, and the simple and already-popular "bang it on the side of a large metal drum" method of getting the seeds off can be used.
The only difficulties left are in getting the metal drum to follow you around the field, and in the winnowing. The first is easily solved with a small cart and a cow or a donkey. Or you could push it yourself I guess, every ten feet or so. Winnowing I think is not much of a time/energy consumer as long as you wait for a suitably dry and windy day.
I think that with this method, the growing of wheat, oats and barley is made just as practical small-scale as growing field corn (maize) is. Winnowing and shucking can be called comparably difficult, I think. Also you don't have to nixtamilize wheat/oats/barley like you do with maize. Maize will kill you slowly if you try to survive principally on it unnixtamilized, did you know. Also I think it doesn't taste nearly as nice to most people. And it doesn't like chilly places.
And If you are thinking that growing them this way will drastically reduce yields, I beg to differ. Grains are grasses and grasses love to grow in clusters. Take the wild rice I mentioned earlier for instance, or the crabgrass that probably grows in your garden. Also, plants generally do a good job of spreading their roots quickly over any available area, and in growing their leaves so as not to compete for sunlight with their own kind. I'm fairly certain that yields would be comparable to broadcasting.