...."And IMO it is not good to advise someone to sell(or even give away) a "hot" hive."
Cao, I just don't yap my mouth without the experience to back me up. Having bought 2 aggressive hives in my first season and dealing with one last season, I already know the psychology that one has to go through in handling a hot hive. Even with experiences, it stressed me out alright. And with newbie without the experience I can see the fear of being sting again in the yard. Not going out will not solve this problem at hand. Not sure if there are neighbors nearby involve either.
If Rock follow my advice, he will be less stress out with beekeeping. If I'm in his situation or facing another aggressive hive in the future, I would do the same thing. First and foremost is to get rid of these aggressive hives. The stronger the splits, now 3 hives, the more aggressive bees will be issued (within 1-2 weeks) from these 3 hives. Now instead of one hive, he has 3 hives to deal with.
That is why I recommend to get rid of this aggressive hive on CL ads; give the buyer this queen also. Then he can get another hive with the gentle type bees to keep. This is the fastest method to tame these stinging bees in his yard. Been there done that before!
The flying bees will go inside the gentle hive and with the queen they will calm down also. But if he want to explore the option of bringing in 2 mated queens trying to calm the queen less hives down then it is his choice. For sure, if he does not get rid of the original queen or break it down to only 2 frames of bees, then they will sting again when this hive grow more in the future. The aggression will never stop until you have break them down so that no more foragers are issued.