How to role play FFM threesome?

Throw away account.

When we first started dating, my wife had floated the idea of having a threesome. After talking it out, we never acted upon it because we both decided that we don’t think we could get over the jealousy of seeing the other with anyone else.

Fast forward many years, we’re both still extremely turned on by the IDEA of a threesome, but know that we shouldn’t engage in the actual act.

We want to try role playing it so we can at least still explore the fantasy. The MFM threesome is pretty easy to simulate, but we’re trying to figure out a way to simulate the FFM without buying a sex doll, since the idea of me humping a toy turns the wife off.

Anyone have any ideas?

Thanks in advance for any suggestions!