We just use a flat wide scraper, both sides. We do not bother trying to clear the grate. Especially not with a tool as it only takes a minimal bend to change the spacing and allow problems later. When they need the space, The bees chew and remove the wax that is left. Figuring, if they can put it there, they can also remove it.
That said, the boiling water bath is the proper way to do it if one wanted an as new excluder.