There's not much you can do to avoid them in the lee, but I have found that the smoothest area, if you get stuck (because it's inconvenient to keep changing valley sides sometimes) is to ride the backlash formed by the wind curling back toward the peak after it has gone over the top. However, you need to be *very* close in (like about 6 inches!) and is dangerous for that reason. 25-30 kts is my level for canning trips.
If you can see down the upslope, then you will be above the demarcation line.
Phil