I had my van repainted this summer and the bodyshop had a sand/beadblasting
unit that they used for removing superficial rust and cealning out the
bodyseams.

It was roughly the shape and dimensions of two shop vacs stacked one upon
the other. A hose bundle  delivered the abrasive to a head unit which looked
much like a circular brush attacthment for a vacuum cleaner. The bristles of
the brush kept most fo the dust from escaping, and a vacuum would draw the
particles back to the main unit.

The brush head unit would pressed against and moved over the area to be
blasted.

I didn't see it in operation but it did do a good job on the "liver spots"
that my aged van had developed.

Alistair