I use the something hard and cylindrical (heh) like a dowel or can of shaving cream, and roll in on the tube like a steamroller toward the opening. That does a pretty good job of getting it all.
The only way I have found to get more is to cut open the tube, which honestly I don't do because it is not worth the effort. There is so little left in the tube after I "steamroll" it, that cutting it open would probably only give me an extra day's worth of paste.