Oat studying

Hey!! I graduated with my bachelors last year but had prerequisites to finish so i’ll be done (officially) this june. I was wondering if anyone had advice on studying for the oat while working full time. I ideally want to start my application after I finish my classes in June, then take the exam 3 months following. Would this be manageable while working full time? I’d have one day off throughout the week and the rest of the days would be 8:30-5 pm. I’m concerned if 3 months would be enough time or if i’d be able to study while working.