ya sandblasting is not a good idea,dont thinki would use a pressure washer either
them things will take the paint off of steel siding,atleast mine will.dont ask how i know
i would put it in the bathroom and take a looonngg hot shower and just let the cambium get damp and loose that way
or light sand or steel wool or just leave it,looks cool.done a few hick bows like that
have a stave of hhb in the house right now,when i start debraking it i know cambium will be left on
this is just as bad as the one your working on to get rid off all the cambium