My new strategy to fend off the beggars went beautifully on my last reach, and it was so simple I can't believe I had never thought of it before: I simply did not look at their face and made pretend I could not hear them, even from three feet away. With zero exchanges between us, it's the quickest and easiest way for them to leave me alone.
Don't look at 'em, don't talk. It's brilliant.