****Q**** I think I am a pretty good flycaster, but when I have to pick up a long line, I never seem to do it well. Is there some method or trick that I should know?
Yes. Your line will go in the direction the rod tip speeds up and stops in the final moment of the cast, so never bring the rod up in a vertical motion. Doing so during the speed-up-and-stop applies extra force or speed, causing the rod tip to dip down and back. This will produce an outsized loop and a sag in the line. Then you must eliminate the sag before you can make a forward cast.
What you need is a straight backcast so that any forward movement will bring the fly forward. To accomplish this, lower the rod tip almost to the surface. You are going to make a side cast, so tilt the reel so it is at 45 degrees. On the backcast, use only the forearm to bring the rod tip and the line straight away from the target and up an imaginary ramp, making sure the rod remains below the head until it is beyond the body. Now the rod can stop while it is rising, and a straight backcast will occur.