For my personal shaving strategy, it doesn't really matter much that I go precisely WTG, so I just go North to South for the first pass. During the second pass, I pay more attention to grain direction, since most parts of my beard will only be completely smooth once I've attacked the whiskers accurately ATG. So the second pass goes mainly South to North with several compensations for a more precise ATG direction.
Where the lenght of the razor does not allow the precise ATG guidance of the razor, I compensate by scything in the right direction.
A partial third pass deals with some spots that usually require special attention. At this point, I concentrate on grain direction the most of my entire shave. I never really bother with XTG.
That's how it works for me. I have noticed that shaving strategy is a very personal affair. The shaving motions are merely a means, not a goal by themselfs.

Best regards,
Bart.