I read the first page of responses . . .
A few things . . .
It is not as hard to setup as you think. It just depends upon your criteria. Want 6 male models - well good luck with that. Want 6 guys under 25 - well good luck with that. So what you base your expectations on will be the main hurdle in how hard it is. I have setup numerous gangbangs. I have done this for my wife and for a few other women. Why? Because I have built relationships with these women that they feel comfortable enough to explain what they want. I know about 25 guys to pull from. Most are single, some are married. Once the woman tells me what she wants, generally with her husband there, I tell them no problem - I will make it happen.
The largest I have done is 7 guys for a woman. But I have one woman right now that wants a dozen. How did it work with 7? Kinda interesting. Seven guys and one woman, no fluffer means you have to get your own wood. I just talked to the guys and told them the rules. I said she will start with 3 guys and then when one cums, he leaves and another goes in. This worked out fairly well because the woman at times had one guy up to four guys and when the other guys were not fucking her, they were in another room eating and talking and watching porn.
The way to invite is also really simple. Every guy knows how I work. I will tell them how many I am looking for. They know that once that number is hit, there will be NO more. So the woman that wanted 7, I invited 10 that I thought would be a good fit. Once I hit 7, I told the other 3, too late. The guys also know that if they say yes and do not show, then they are out of future invites. So if you say yes, unless something really big happens, you will be there. In doing this for years, twice has there been an issue. One time a guy got hit in his car and sent me a video of the car going onto the tow truck. Another time, the guy was a fireman and got in touch with me that morning when he got called to a big fire out of state.