I'd agree with that. 'Babbling' works like a charm for me, too
I'm rarely pulled over and on occasions when I have been I have obeyed the command and then been motioned to drive on before I get near enough to extend a hand for a handshake. However, I'm female, so that might have something to do with it.
The other thing I've seen work (in the daytime) is deliberate 'kangaroo' jump or stalling of vehicle followed by clapping hand over mouth in a 'lordy what have I done' gesture. Seems to work for female drivers maybe because it puts the gringa in the role of stupid driver and thus lightens the tension and everyone laughs.
In summary display friendliness, openess, self-confidence (unless stalling vehicle) and interest. Do not display fear, concern, guilt or anger. A 'worried' gringo face is often mistaken for a 'guilty' gringo face, or at least one that can be taken advantage of!