Gang Bang the Sissy

Host a party with only girls and make everyone wear a strap on, blindfold him and make him suck each girl and guess who it is… then surprise him by having one guy at the end (also blindfolded)

This is first of all, an incredibly humiliating experience as he will be forced to give a blowjob to the strapon of each girl at the party, completely emasculated and acknowledged as a sissy girl.  Then it will be even more humiliating and when he's forced to suck a real cock in front of all the girls; effectively making him a forced bi-sexual in front of everyone.  Properly executed, this could be the ultimate public humiliation... and if he is blindfolded from the very start, he will never know who was there, which girls he sucked, and which cock he sucked. 

You should explain to him that he will be forced to suck each strap on until you tell him to stop.  You should noticeably whip him now and then so he continues at a good fast and effective pace.   Tell him that you will not tell him who was there, but that it will be at least 3-4 girlfriends that know him well, and that he might never know who they are.  That will drive him crazy.  You should explain that several girls have confirmed they are coming.    When they are there you should have all the girls touch and caress him at the same time so he can feel there are several of them in the room.  

He should be in chastity and he should be blindfolded so he can't see and he should have earphones strapped on to his ears and music continually playing for the whole night, so he can't hear either.   You can then dress him as you want (as a sissy or completely naked).  

You need to plan this well in advance, after you have already had him suck your strapon several times and you have communicated to him that he seems to really enjoy it.  It should be a party that he knows he will have to serve at, and that only women are going to attend.   Prior to the party you should apply the blindfold and ear-phones so he doesn't see who's there or how many people are coming.  Just tell him at least a few days in advance that he should be prepared to serve the woman and be prepared to show how good he can suck cock.   

You should invite at least 4 women over who are friends from the fetish world.  If they want to come as a couple, you can organize for all the men to have the same treatment as your sissy (blindfolded, with earphones, and ready to provide service).   None of the men should ever know who attended under any circumstances.  The women should be provided a strapon and should be prepared to tease and play with your sissy and the other men (if any).   These women should never ever reveal who they are... it will be a secret that will haunt your sissy every time he sees one of your girlfriends.   Therefore, all your guests should leave before you allow him to see or hear anything. Effectively, it’s as if he was humiliated and sucked cock in front of everyone of yours and his friends, because he will constantly wonder who was there.    

Be sure that your sissy and that no other men have any way to see or hear what is happening.  You have to be convincing and confident, making sure each women plays along.  You should definitely have plenty to drink for everyone, so everyone can be in the mood, and also provide a dark, candlelit ambiance with nice music.