Question about AC motor brushes

[intrepidity]

8. Oh hey, another question if you don't mind

I notice the armiture and housing are prone to rusting. I'm pretty sure I can gently sand that off (is 150 grit too coarse?), and I understand that I must meticulously brush/vac/blow any debris out after, so no metal particles lodge in an unfortunate spot. But can I apply WD40 to those pieces carefully before reassembly?

I will soon know whether it's ok to submerge the whole thing in Evaporust--well, technically it surely works well at removing all the rust--it remains to be seen whether the motor will still function.... I've tested continuity between all pieces (adjacent commutator bars; diagonal bars; bars to armiture; any more?) and everything seems ok.

I've been intimidated by motors my whole life, so this is an adventure.