Select an oil or blend of oils that is non-caustic and not soluble in water. Make sure that the oil does not contain any type of wax. Mineral oils and most cooking oils are good options. Cover the concrete form or mold with a generous application of the oil using a paintbrush. Use a smaller brush to oil tighter areas. Keep the application as even as you can. Pour the concrete necessary for your project. Cure the concrete as appropriate. Carefully remove the mold or form when the curing is finished.