>>3280158Use a small rangefinder or mirrorless with a wider-than-50mm prime. Stop down and learn how to zone focus. Then just wait for the moment, get in close, snap and move on.
Of all that, I would say using a wide prime and zone focussing are the most important bits. I get pretty good results using a 14mm manual focus lens on my Nikon SLR. It's not compact, but it works.