Door: kelbytv.com/photoshopkillertips
Keep the liquify tool running fast by isolating the area you are using it on.
http://kelbytv.com/photoshopkillertips/2010/06/07/a-faster-liquify-tool/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+PhotoshopKillerTips+%28Photoshop+Killer+Tips+%28Video%29%29