I took a risk and sprayed mine with PB B'laster a few years back. It made a significant difference, maybe 80% of the way back to new. It's still pretty smooth today, and hasn't ruined any of the paint/finish.
If you try this, use plenty of paper towels to keep the spray off the screen and keyboard, and keep the computer on its side for each hinge, so gravity carries drips away from any other components. Give it some time to dry, then hold paper towels directly on the hinge and invert the TiBook a few times to get any other drips to come out. After a few cycles of opening and closing the lid, it should hopefully feel easier.