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I'm afraid it is not easy (or impossible) to find a liquidator who will cherry pick, because picking the best ones (or the 'black ones') from the pallets will limit the value of the lot to be passed on to the customer, in fact, liquidators will often declare that they do not cherry pick their items to assure customers and to attract more buyers. But you can actually confirm this and ask them. And yes, the only possible source of most of the brand name goods/shoes would be liquidation, and they come in mixed lots.
Let us know if you need further help.