Choose a wood finish product with a mold inhibitor if you live in a wet climate. If you live in a hot climate, choose one with UV protection.
Clean your chair with a pressure washer or with a soft brush and a good wood cleaner.
Allow the Adirondack chair to dry completely, after rinsing thoroughly.
Place the clean chair in a work area that is protected from the elements. Prime it with wood primer, using a 2 1/2-inch paint brush. Use a 1 1/2-inch brush for good coverage between slats, legs and tight spots. Moisture can easily wick into the wood if it is not thoroughly protected. Allow the primer to dry completely.
Paint the Adirondack chair with an exterior enamel, using a 2 1/2-inch paint brush. Again, get good coverage between slats, legs and tight spots by using a 1 1/2-inch brush. Allow the paint to dry completely before removing the chair from the protected work area.