Place flour and bread crumbs in separate shallow bowls. Drain the shrimp in a sieve over another shallow bowl to capture the buttermilk. Dip the shrimp into flour to coat, then dip in buttermilk, and finally dredge in bread crumbs. Fry the shrimp in hot oil in batches until golden brown, about 3 minutes. Drain on paper towels to absorb any excess oil.