I have a SOT. One tactic I like is to sit side saddle with your legs dangling in the water. This creates some drag and slows you down a bit. Then the presentation is to cast "upstream" let the fly sink till you are about parallel to it and start the retrieve. I have also used a drag anchor (just a length of chain) but found it to be only useful when you have a long drift to make otherwise its a pain.
How does the drift sock work in a heavy current? I was under the impression that it was a tool for slowing you down if the wind is pushing you. How big of a sock do you use?