Before using the very expensive Boeshield T9, you should apply a generous coating of either naval jelly or hog snott (motorcycle rust remover) and let the pink jelly sit undisturbed for 20 minutes. Then remove the "pilled up" rust with WD40, a putty applicator and a scotch bite abrasive pad. I WOULD NEVER APPLY SANDPAPER TO THE BED OF MY LATHE, but there are many opinions on this.
If the first "snott" application did not remove all the rust, keep repeating applications until all rust is dissolved. TAKE CARE TO KEEP THE PINK JELLY OFF OF PAINTED PARTS AS BOTH NAVAL JELLY AND HOG SNOTT WILL REMOVE PAINT.
AFTER all rust has bee removed, clean again with WD40 and towel dry. THEN apply one generous coat of T-9. Allow the Boeshield to dry completely, then apply a second coat.
Then a monthly re-application of T-9 should keep the rust from reappearing.