Since the High Speed Silver was paint, you should weather it the way you would weather any other paint scheme. They were kept very clean, so for mine I used a panel wash only around the opening/removable panels and hatches, and left the rest of the airframe pristine.
In your larger scale, though, some subtle repainting with a slightly different silver color around fasteners and removable panel edges might give a good effect, as well as some scuffing where the pilot and ground crew step. I'd expect that the gun panels and large engine hatches would get the most wear and tear.
Peter