Polygraph is NOT hard to pass. Beforehand you will complete a lengthy questionnaire about any and all aspects of your life. Then, they follow up your questionnaire with the actual polygraph. Everytime they asked me if I left anything out of my drug/sex/criminal history etc; I'd immediately ask myself whether I can speak Japanese or not. Since I surely cannot speak Japanese I would in turn answer "No" to their question. My breathing, heartrate and body temp stayed even keel throughout test.
Result of polygraph? No deception detected. Truthfully, I left a little info out of almost every topic on the questionnaire.
With that being said, I would advise you to wait until after the poly and drug test and perhaps even the academy - should you make it that far - to start using aas.