This technique was demonstrated for me by a bartender at London's M&H recently. "Martinis," he said, "make themselves." And he pushed the tin into crushed ice for about a minute while he busied himself elsewhere. Some Japanese bartenders I've worked with believe that, beyond just chilling and diluting, stirring techniques are crucial to binding flavors together, a concept that was new to me at the time. Their explanations reminded me of swordsmithing, hammering and twisting and hammering ten steel rods together until they have fused into a single blade. To the Japanese, simply allowing a drink to get cold on ice is insufficient: the ingredients' flavors do not become one. But I'm not sure how much I've ever bought into their technique. <edited for typo>