The secret is to go to them often. I find all kinds of really neat things to use as Foley props. Plus I love the strange looks I get when I buy high-heels! When I was rebuilding the studio after the flood of '07 I found and bought a great condition real leather sofa - for $50.
Yeah, the thrift stores here tend to be very picked over, all the time. I don't have the dedication to go every day or get up early on shipment days. There's just too many people in this city and what with the hipster movement everyone wants cheap/kitchy/ironic/ 'cool'-looking stuff.