On the "Drive Shaft Maintenance" page of Tom Woods website he himself posts that the only way that he knows how to grease it is to remove the shaft, at least at the T/C end. He also shows a picture of the tool, which I assume is the tool he supplies with a new shaft.

I have to wonder if it is not possible to drill out the centre yoke housing into the centre pivot point, tap a thread into it and fit a grease nipple of your choice on the outside of the yoke. Maybe you should take it up with Tom.

He also makes some recommendations concerning grease.