You can add oil through the axle where the bell crank sits; it will eventually work its way out past the cones and/or the bell crank. Whether this is a Good Idea or not is questionable if the hub was designed for grease lubrication.

You can add an oil port without tapping. The plastic Sturmey-Archer oil port cap is press-fitted into the hub shell, but if you drill a hole in the shell be sure to remove the mechanism first so metal debris doesn't fall into the works.