Drifting in fast current is a whole different kind of drifting then what we are doing here. I have read a number of good catfishing articles on drifting in fast water. There is an excellent article in the January 2006 In-Fisherman magazine titled “Controlled Drifting for Catfish”. There is another drifting article in the August / September In-Fisherman magazine titled “Bull’s-Eye Blue Cats”.
Most of the articles focused on fishing below dams. The trick is to use your trolling motor or outboard to slow drift or slip down current just slower than the current.
You need enough weight to get your rig to the bottom on a tight line. Once you touch bottom you will lift your bait 3 to 6 inches off the bottom , letting the current slowly carry the sinker a few inches downstream. You use this lift and drop technique to feel the bottom and maintain good bait presentation. It is kind of a “feel” kind of thing – you don’t want your bait rig to drag on the bottom or you will get hung up. You drop the rod tip, feel the weight tick bottom and lift to keep your bait in the zone.
I would recommend you get a copy of those In-Fisherman articles and give that a try. It sounds like these are some techniques that might work in your situation.