I have tried it after a fashion.
When I did this figure
I primed the whole thing black, then drybrushed the fur and flesh progressively lighter grey to an almost white.
Then I washed the fur with thinned Badab Black and the flesh with alternate coats of Gryphonne Sepia and Ogryn Flesh.
If you keep the washes thin enough, the highlights come through really well and will take just enough of the wash colour to make it look right.
I did a few of the other beastmen in a simialr fashion, but using brown rather than grey as a base. They can be seen here:
http://leadadventureforum.com/index.php?topic=20619.0So far its been my only experiment with zenithal shading/highlighting, but I found it really easy and quite effective, although given that you have to use three or four washes and let them dry inbetween applications, I'm not convinced its actually any faster than the normal painting method.
Hope that's useful to you.