After some reading: It is a weak alklali and can have a slight bleaching effect if wet. It is best used dry, as this following artilcle link explains, for eradicating them. Part of it's effectiveness lies in its mechanical properties, as a crystal on the cockroaches exoskeleton and also it ingests the poison when the insects preen themselves removing the boric acid dust crystals from their bodies.Given this fact, I would prepare and apply the powder exactly as recommended in the article, or as as closely as you can, to maximise its effectiveness. I wouldn't worry about using it dry on those surfaces; maybe, don't apply it to those surfaces in sunny areas of your kitchen; the solar rays may have an unforeseen effect.
https://entomology.ca.uky.edu/ef614