Having used Torpedos on many old bikes, I'm pretty sure what you need is to lubricate the insides of the black plastic thingy, but also the cable itself. So stick the long thin nozzle of the lubrication can between the cable and its coating and give it a good, long squirt. All places you can get to. Then switch gears from 1 to 3 and back a dozen times. Hopefully, disgusting black-brown sludge comes pouring out.