Whenever he disobeys you, and after you discipline him for doing so, give him a more inconvenient reminder to make sure he understand he should never do it again by making him wear a bra for at least a day.
This should be perceived as a punishment and reminder of your authority. You should not allow him any exceptions if you threaten this…you should follow though and be very strict on this, no matter what he has to do that day. In the end, he will definitely remember to correct his behavior.
Remind him why he has to wear a bra and how much time he has left on a constant basis. Make him repeat back to you what he's learning from this lesson. Ask him if he thinks the punishment is fair, and then tell him you don't care what he thinks.
When you are punishing him, tell him that tomorrow he will have to put a bra on and will have to keep it on until a certain time. Tell him the night before so that he has time to think about it in fear. Then follow through with it. This is a good day to also take him to the tanning salon and have the bra marks tanned into his skin, so it provides a lasting lesson until the tan goes away.
Don't let him talk his way out of the predicament or convince you that your punishment is too harsh. You should enforce this and any other punishment strictly until you see that he has learned the lesson and will definitely correct his behavior.