I use the 3 x WCA method and it seems to work out OK.
As for determining the WCA, I use the following method
1. Determine the amount of drift for full crosswind (ie on a 30knt day in a 180 knot aircraft max drift will be ~10 degrees)
2. mentally overlay the wind direction on the DG and use it like a whiz wheel using +- the drift angle above.
Difficult to describe without a picture.
Bevan..