Re: casting weighted flies
All great info here. Another way to help this out is to position yourself so that very little false casting is needed.
For instance, if you are drifting a nymph through the bottom of a run, position yourself to the side of it instead of below it. While fishing it from below, you have to strip lots of line in and work it back out for the next drift. Lots of opportunities for tangles there. If you're fishing it from the side, you can cast quartering upstream, maintain the line during the drift with mending and rod lifting. Once its quartering downstream, point your back-cast perpendicular to the current, and lay it down again quartering upstream.
Maintaining a dead drift from the side is indeed trickier than from below, so you might want to brush up a bit about mending and reach casts and such.