That's one way to do it. You can kinda "speedrun" some of the initial changes by going commando on the first day as secretary to get the sissy underwear then show up in casual clothes the next day to be given the androgenous outfit. Get locked in chastity the next day by doing nothing about your arousal up until that point.I think you just disobey Antlers and that's it, she gives you the clothes.
I wanted to keep my response as general as possible. You can be obedient the entire game if you want.