The problem now is with the different agencies not standardizing the signs. The basics are pretty universal, but where in my experience it is flawed is showing what your psi is and what depth you would like to do your safety or deco stops at. I've have come across at least 10 different ways to describe psi. It is further complicated when you start using your light for signaling. Now when diving with a regular partner you get to know the different signs. When you introduce and unfamilar third or fourth buddy, that's where mixups occur.
My advice is to go over all the different signs that you and your buddy team will use during your pre dive talk.
My advice is to go over all the different signs that you and your buddy team will use during your pre dive talk.