What's the hand signal for arguably the most important day to day instruction: cleared to push back? We all know how to work around this, we all have our special signs for that and generally the ground personell undertsand, but is there an official signal? Have not come across one yet!
Anyway, to answer the first post, in my experience, the ground crew are well versed in everyday hand signals, so no complaints there. New FO's are usually a bit amused the first couple of times handsignals are used, since it's not an everyday occurrence. Now of course headsets are safer. But that doesn't mean that hand signals are unsafe.