Different but similar for us. Our fun with adding another guy just kinda happened one night, drinking involved. Was over quick, he left and wife cried and apologized over and over, my emotions were a mess also. Our sex was great for a few weeks after. We talked about it and invited him over again. Just about the same deal, drinks, he did her over the back of the couch, 3 minutes start to finish, he left. She cried, apologized but we had goooood sex an hour later. Just kinda worked up to doing it more often. Were comfy with it now and we all have fun. They click well, it's fun to watch them, he likes watching us, she likes us taking turns. She and I do get some weird feelings, especially me but it's very obvious she likes the sex.
We did hook up with a stranger once, in the bar leading up to going to his room was so damn exciting I thought my wife was gonna melt but once we got to his room it just fizzled out. We were very nervous so I'm sure that's why it didn't go well.
With out friend we know what to expect, we look forward to it, we don't use condoms, we dont play with the sperm but the mess is part of the fun.