I've been using Style's best friends test to transition from my openers a bit lately, its a good routine but there are certain situations where the following alterations/additions are useful.

To account for the (quite regular) situation where the two birds don't look at each other after you ask them if they use the same shampoo you can use the following. Basically if one girl looks at the other and one keeps eye contact with you, cold read the one who keeps eye contact as being the dominant one and the other chick as the submissive one, can be a nice neg too if needed.

If neither of them breaks eye contact with you pull some crap about them "obviously having a connection, but both being very independent people".

It's also nice to explain what the different reaction would have meant, so that "they can use it on their friends blah blah".

It's also beneficial to add a sub thread somewhere, something along the lines of "a girl I went out when I was staying in Mexico last summer was into psychology and taught me this" is a nice DHV with obvious thread attached, making it easy for the HBs to continue conversation if they want.