My preference has always been 'nothing'. Graphite is excellent for points mentioned, but I find it overused and very messy.
If a mast is properly cleaned and dried before storing, it makes all the difference. I have pulled open a mast at the Unit before exercise and find someone had it stored wet, and then there is a good chance it will freeze as one piece before deploying it outside in winter.
If the mast is really soaked, then graphite makes little difference in the freezing temps.
My :2c:
ME