I've taken the Coast Starlight from LA up to Seattle (it was 5 hours late going and 13 hours late returning :O).

If you can live without mascara, give it a try. You could probably apply it during one of those long waits for the freight trains going by but it wouldn't be a good idea to apply it while your own train is moving.

Even if you get used to the swaying, there always seems to be a burp in the line when you least expect it.

Enjoy your trip!