phosphate coating

[PeteyAce]

there is apparently a phosphate coating on the spindles of the pinion gear hence why it didnt go down all the way for me onto the pinion yoke, ford racing tech told me to hit it with a drill with a wire bursh attachment, i had a dremel tool but i dont think its doing the trick, anyone have this problem? and is the pinion nut only suppose to go down hlafway becuase it goes down fine for me until i hit it half down then it starts to tighten up