Tinny -
I agree with you and Checkboard. In flight, you suck it and see! Then nail it down. As long as you are maintaining track, using either ADF or VOR, then drift is the difference between heading and track.
What I can't understand is why anyone would would want to do arithmetic on the ground, or worse still in the air, to calculate a figure that is bound to be wrong, and is likely to change significantly througout a flight and approach.
Of course, I would agree it's helpful to know where the wind is coming from, but you find that out pretty damn quick in any event!!!
So many people have given methods of calculation, using watches, DIs, etc that there must be some sort of rationale. I am concerned I might be missing out!
Someone, please enlighten me on why they want to do this by calculation rather than by finding out by flying the needles, and put me out of my misery!