How to remove husk from grain?
Brewer's spent grain should have already been coarsely ground and mostly separated from the husks, so a basic winnowing method could be used: Fully dry the spent grain, then use a blower from below, or sprinkling the grain through an air current, to blow the husks away from the rest of the grain. Yield levels will likely be quite low because chunks of the seed will remain attached to the hull, but if you're working with brewer's spent grain, you likely have quite a bit to work with.

Note that the most common uses for spent grain are composting and as livestock feed. While people have tried using it in baking, the low starch level means that it can only be used to replace a small portion of the flour.