Before we started dating I knew my GF in college and I knew she was a slut. She had a reputation, and I'd known some guys who had fucked her. When we got together she was pretty ready to settle down, but I told her about hotwifing/cucking, and that it turned me on, and she seemed pretty happy about it.
The first time another guy fucked her while she was with me, she had told me about a MFM she'd had and how good it was. I asked if she wanted to do it again and she said yes. So we went to a club so she could find someone she liked, she danced with a few guys till she found one she liked, then went into total slut mode. She was guiding his hands all over her body, up her dress, on her tits, grinding on him. He nudged her panties to the side and fingered her a little bit, but she turned around and said something to him, at which point they came over to where I was. She introduced him briefly, and said he'd be coming home with us. apparently she'd told him the plan and he was cool with it. On the way back we set out basic ground rules. He uses a condom, he stops when we say so, he leaves when we say so.