Depending on how many male plants you're going to have, it could vary the ammount of work your going to have to do. If theres a slim % of males it only involves possibly 20-30 minutes of work, but if most of them are males then its going to be a tough job. Also keep an eye out for them, you wouldnt want even 1 to sneak by your eye, so I suggest as they age and show sex, check off wich ones you know are female on the graph you drew, so you dont forget wich places to check.