I used to wait from 10 to 60 sec after the boiler elements have switched off. The shots were pretty good, but I never really zeroed in on an optimum. Besides this will change depending on what beans you are using. Light roasts will need hotter (ie shorter waits) and dark roasts longer. I dont think there is any best method. If you brew with the elements on, the temp climbs pretty quickly, so you have to be quick to use this method.