I use it ALL THE TIME. It is the most awesome way to disagree with someone, ever.
There's no real great way to do it in actual manual ASL, but a smooth gradual transition between nodding your head "yes" and shaking your head "no", combined with appropriate transformation of facial expression, does the trick discourse-wise.
Julie always gets mad at me for starting every sentence with "right, but" (in both English and ASL). This is a similar but nonidentical expression. "Right, but" expresses that while what your interlocutor has just said is true, it has failed to account for some major point that you are about to bring up. I'm not saying there's anything wrong with "right, but"; I'm just saying it's a different kind of statement than "yeah, no".
"Yeah, no", as opposed to "right, but", does not imply that the content of the interlocutor was correct, but merely that you have understood what they meant and are now contradicting it. Surprisingly, this is not necessarily a hostile position to be taking- often, in my experience, "yeah, no" is employed to acknowledge that the interlocutor's position makes sense and would be a reasonable assumption, but in fact does not obtain.
For example,
A: I'd heard of the Barefoot Benefits and all that stuff - here, no less, with that fingery-shoe conversation - but I didn't realize that by "barefoot" they meant "nothing to do with bare feet whatsoever, but rather walking on barrels like an idiot".
B: Yeah, no, these are a different phenomenon from the barely-there shoes that hippie lifeguards like.
One of my favorite undergrad professors did a really fantastic super-subtle version of this: in class, when anyone was talking, he would thoughtfully listen and nod as you went. You would gain confidence (the professor is nodding thoughtfully!) and so expand on your thesis, often to somewhat absurd little thin branches (the professor was a Professor of Art History). Finally, having concluded your analysis, you would sit, quietly, while the whole class waited and the professor continued to nod thoughtfully for a few moments.
Then he would sit up straight and say "No, I don't think that's right." Then he would tell you about how wrong it was for a while.
I loved this professor greatly, and I think everyone else did too. And I really appreciated the fact that he thought carefully about even the dumbest, longest, most hare-brained expositions about art. He thought about them carefully, nodding all the while, and then, very politely, shut you down good.
Yeah, no.
