Hi Tom, I guess the answer to this is yes *and* no. Although we don't tend to use it much for its gloss properties, RW4 is highly polishable and can be taken to a mirror gloss, in the same way that a hard wax (such as #8 wax) can, so from a perspective of the glossiness of the surface, yes, RW4 will certainly 'gloss up' the surface of sheet wax.
That said, the problem with the surface of sheetwax is generally not its glossiness (although - for sure - it's not glossy), it's more a case that the wax itself, and the application process of it, tends to produce a very subtle, but detectable, undulation in the surface. My suspicion would be that application of the RW4 onto sheetwax will definitely make it more shiny (and massively improve the way that the sheetwax removes from the mould) but is unlikely to make the surface much flatter. The end result being shinier but still imperfect.