Lime Sulfur (calcium polysulfide) is both a traditional and excellent fluid to protect and bleach deadwood.  You can tint it with black India Ink to produce a more gray-toned deadwood.  The best way to do this is to use a small plastic cup, add the lime sulfur, then add up to five _drops_ of India Ink.  It does not take much India ink to make the lime sulfur dry to a gray tone.  Lime Sulfur can also be diluted at a 10:1 or 20:1 (water:lime sulfur) as a fungicide and insecticide during winter dormancy[1].

[1] Do *not* use as a fungicide/insecticide for overwintering Satsuki and other Azaleas.