Apart from the FF pages of duos, plenty of escorts mention FFM meets on their solo profile pages (although I think they are not supposed to over-discuss this on a solo page under current AW rules; SPs on here might confirm). Sometimes a separate duo tab, sometimes a list of partner links at the bottom of the page, sometimes a mention in the FAQ section. If you keep looking at escorts you fancy you will come across these.
The safest way to organise is probably to see such an escort that appeals, and then if you have a good time discuss a duo meet in the post-action chat. Of course, you are the paying for two meets, but probably better than diving in with two escorts you don't know for what will probably be a sizeable fee.
Finally, be clear in your mind what you want. Lesbian action? Both concentrating on you? PSE? Sub/dom? Roleplay? etc. Doubling the number of women increases the options/variations, but also increases the chances of being disappointed if you make the wrong choice.
