No recent experience but here is how I used to do it.
I started with a standard sink tip line and heavy, weighted fly. What i found was that the fly would often snag up, so i tied them to fish point up. This helped no end, but I was unhappy the fly was just bouncing the bottom rather than swimming!
So, I switched to a Teeny T 200 line (5.5 inches a second sink rate) and tied my flies so they where almost neutral density. This was achieved by using man made fibres and good quality hooks that where light weight but strong. Since those days i have discovered EP fibres. The "Slinky" version would be superb for small minnow and bullhead patterns. This stuff is so mobile and "alive" in the water.Perfect.
The T line got the fly deep and then the lightness of the fly meant that it would flutter and dart around with the current rather then drop between rocks. Its exactly the same principle I use when Pike fly fishing in rivers.
I have had a few big brownies by mistake in the winter and autumn when pike fly fishing, so i guess the Brownies will hit fish pretty much anytime as i used to fish the spring on the Don for them...if that makes sense.
Hope that helps a little
Rob