Er...vary the amount of crab? Out of interest how would you land a 25m span glider in a strong xwind? Genuine question.
Yes you can vary the amount of crab - personally I have always found that doing this is a LOT less instinctive and slower than varying the wing down and leaves a low hour pilot behind the aircraft.
If you read some of my other posts on this subject (possibly another thread), you will see I have always pointed out that you use correct technique for the aircraft you are flying so yes, I would use more crab for the glider, though most gliders the wings have a fair amount of dihedral with the wings mid level so not quite the problem you seem to imply - probably less so than say a Pa28!