Or you can opt for the slightly better-reviewed professional-grade Koriko Hawthorne strainer. You can buy a fine-mesh cocktail strainer specifically for bar use, but if you've already got a small ...

Attach the Hawthorne strainer to the top and then pour the liquid into another ice filled cocktail shaker tin. Swap the Hawthorne strainer to the other tin and repeat the process 5 times to and fro.