Just had an idea, what if you masked the scale while you still had it on the blank? You'd just need a row of crescent shapes cut out of stencil material, move on down the blank with whatever highlight you choose just like you would using the half circle stencil. Or spray the highlights first in rows then adjust your scale to match and shoot transparent enough to see the highlight? I won't be able to get any painting in til next week or I'd try it!