A 3some (FFM) is not hard to find, you pretty much just have to ask for it. It will be made easier if you see the same girl a few times first, then ask for another girl to be brought in. Smile is best known for this special request as already noted above, but there are others. Best to stick with the veterens as they are driven more by money and have overcome most embarrasing/unique situations in their years of work. The less experienced providers may be a little uncertain or afraid of the experience. Mostly new girls at Smile (was there yesterday) so not so sure, but Holly would be the person to ask. Not to digress too much, but there were some real winners at Smile and even at Oceanside in the past who did not mind 3somes and boy oh boy, they were fun as well. With the economy the way it is and the increase in LE activity in DFW, alot of the girls seem to be more careful and rotating in/out more quickly. Holly, yet again, is rare in that she has been at Smile about 2 1/2 years and has shared time with a lot of guys/girls. Tiffany and Cindy are also 2 seaoned pros with some mieleage built up between them so you may want to start there.
Now, a 3some (MMF) may be a little more difficult to arrange. Never tried it and never asked for it but I would bring it up during your next visit. I would stop at Smile for this request and talk to Holly to see her thoughts as I'm sure she'll be honest with you and will give you the temperature of her "co-workers" as well.