Hello India 42!
Nice to hear from another tuggie!
I know they must do things differently in California! We certainly agree that no signal is better than one the glider on tow will probably misinterpret! And over here in the UK asking the tuggie to waggle the rudder at low level is not a good idea at all at all.
As for communicating with radio, that is asking a lot from an early solo glider pilot who is rather busy dealing with the airtow. Keep it simple! Just drag him up! (unless he gets too high behind you, in which case he will be faced with the problem of finding which field, schoolyard, or parking lot is now decorated with a nice blue 180 foot rope with rings at each end.
Early in my career at Booker, instructing in a glider, when we got out of position both the tug and I let go at the same moment. I had to go look for the rope later, on the ground. Thought it would be easy to find again......