Shoe polish (and accoutrements), hair cuts & shaving kit (military for the use of) are all tax deductable as they are considered an essential part of your job. Ask any Bluntie in SHQ, they probably all claim so will know the hows and whys.
However, since the amount you will be claiming back runs into pennies at the most (unless yer polishing yer boots every night) then a quick time & motion study will probably prove it a worthless exercise.