Take the compression tester hose, hook it up to the air compressor, turn the motor until both valves are closed (look at the rockers), put air pressure on the cyclinder, and listen for where the air is leaking out (use a piece of vacuum hose held to your ear and around the valve springs if you have to). If you have headers you'll probably hear it by listening to the tube on that exhaust valve.
If there is no air up top, it's probably leaking down bottom and you might hear it from the oil pan.
If oil doesn't help, then either the rings are completely destroyed or it isn't the rings.