I agree with DC46, especially at a fs place its best if they know each other and have worked together before. If its a fs place and you know mms well then ask her for recommendation - this would be more like 3-way instead of 4-hand.
If its 4-hand massage you are after, then best to go to a R&T place. I have had different experiences pre-flip. Sometimes one works the top half of you while the other massages the bottom have. Other times one does the left side while the other does the right side. After the flip I like one of the left and one on the right. then you can play with the each of them (tits, pussey, etc). You can direct them to touch each other, or kiss each others.
Pricing - idf its a busy place, they may want two house fees. If its slow they may accept one house fee. In either case you will tip each of them.