Agree with the teasing comments/suggestions and always compliment her when you are out. Either genuinely tell her after the event or make one up that she was getting looked at by another man/men.
When you went to the toilet in x did you notice those guys in the corner watching you? They couldn’t take their eyes off your xx. Who can blame them. Then let her reply. Don’t escalate to quickly Doing it after the event is “safe“ for her, nothings going to happen but her imagination can run wild.
During sex that night, laugh to yourself and when she asks you about it, just say, I was just thinking how jealous those guys at x would be knowing I am fucking you/ making love to you, they would be so jealous. Again gauge her reaction.
If you have any friends over, make sure you mess up a draw where she keeps her lingerie/underwear/dildos etc so it’s obvious someone‘s been in there. Casually mention to your wife a reason why x was alone in that room. If it’s the bedroom, looking for your mobile, you searched downstairs he searched upstairs, took ages to find, for example. She will immediately think he has been in the draw when she goes into that night and again her imagination will run wild.
During sex with her using her dildos comment on the size, I wish I had a cock this size so I could get really deep in you, or I wish I had two cocks so I could fill you up at the same time. Imagine that, would you like two cocks in you? You have taken out the other person and it’s just about you having two cocks. Again the situation is unreal and “safe” so judge her reaction. If she seems like she likes the idea start building on it. Turn it onto you so she’s not embarrassed by it. I think you would look great with two cocks in you, the idea kind of turns me on, only as a fantasy of course. What do you think would it be fun?
If she makes you go down on her again, don’t ignore what she’s making you do, comment on it. Wow, that looks like you have been having sex, you taste amazing, this really turns me on. Have you been dirty?
Continue to go slowly....