Maybe this is obvious, but there are mills made specifically for milling barley. They run about $150 new. The Barley Crusher seems to be a favorite, and is ready to mill right out of the box.
Now there's some take delight in the carriages a rolling
and others take delight in the hurling and the bowling
but I take delight in the juice of the barley
and courting pretty fair maids in the morning bright and early