So I've been with my girlfriend for over a year now, and for months she's been expressing an interest in bringing another girl into the bedroom. However, my girlfriend is also rather introverted and not flirtatious, which leaves the "how" up to me. To quote her, "if you start making out with another girl in front of me, I'll join in" seems pretty simple, so lately I've been just trying to game girls normally. Well, I'm certainly no PUA, but I would very much appreciate any advice from the community.

The long story is, that my girlfriend was a virgin when I met her. She's 20 and I'm 30, in case you feel like judging. She knew that I was a "poly" kind of person when I met her, but we had mutually decided to remain completely monogamous for a year or so until our relationship had solidified and we had a strong trusting bond between us. She is genuinely curious to be with another woman, but due to her nature I will have to do the picking up. I really do love my girlfriend and see myself spending the rest of my life with her, so naturally I want to do this with some precision and care. Picking up a girl for her doesn't even have to end in a tried and true threesome, as to me it's only the Pandora's Box to eventually lead to a true polyamorous relationship. My girl is very open minded and devoted to me, she's just terribly shy.

Currently, my plan is to establish a sexual relationship (without actual sex) with another woman, then set up a situation where the three of us will have an opportunity. This does involve some deception I guess, as I will be essentially leading the other girl on to have sex with me, though I do believe that almost all women will experiment when placed in that situation and properly turned on. I do have consent from my girlfriend to escalate (to an extent) on another girl if my intention is as thus. As a matter of fact, I do have a particular girl in mind who I'm 90% sure is attracted to me, although she claims to be "straight all the way". She and my girlfriend have already gotten to know each other as well.

However, I'm open to other suggestions. I'm sure I'm not the first guy to be in this situation. The only two real barriers are A) I can't sleep with the other girl first and B) no anonymous strangers (i.e. picking up a girl from the bar).