Where you need luibe is inside the neck. Even neck sizing, the expander ball is dragged back through the neck, expanding it slightly, and that can stretch the case (if you get a neck-sized case the bolt won't close on, that's why.)
You can use Motor Mica (from any auto parts store) powdered graphite, or do as I do -- I moisten a patch with Ed's Red (a home-mid gun cleaning solution) and simply press the case mouth into it, leaving a miniscule bit of lube right at the case mouth.