I used a teflon dry grease for my cables in Alaska, worked fine down to -30C. Phil tenacious oil is another option.
Yep, grease the contact area between bearing and frame in headset, and threads on the bb during assembly.
Pre-test your intended product in the freezer
![Smiley](http://www.bikepacking.net/forum/Smileys/Lots_O_Smileys/icon_biggrin.gif)