Combine gin, vermouth, and Campari in a large foodsafe bucket. Funnel into a small oak barrel of roughly three gallons capacity. Seal. Let sit for seven weeks, periodically taste-testing the mixture after two weeks. Strain several times through cheesecloth to capture bits of wood and sediment. Store in a glass bottle. Pour three ounces into a rocks glass filled with one large ice cube. Garnish with the orange twist. Recipe makes 128 servings.