NEW YORK — The term “tie-dye” usually conjures up images of hippies frolicking in the Woodstock mud. But Miuccia Prada has other, considerably less rustic, ways of working the process, which give it a more sophisticated, feminine twist. She’s using it for resort, in fact, in tiered dresses, ruffled skirts and little tanks that would suit any young woman on the go. Here, her tie-dyed cotton skirt, worn with a wool T-shirt and quilted nylon bag, all for Prada. For more on the season, see photo spread Soft Sell.