Lay the print face-up on a protected surface. Sand the surface lightly with the 120-grit sandpaper using circular strokes. The goal is to break the surface sheen of the print so the wash will grip; you are not trying to remove ink or damage the image. Wipe away the dust with a dry cloth. The surface should look slightly dull.

Brush the diluted gray wash across the entire print in one direction, working quickly so it does not begin to dry before you wipe it back. Load the brush generously and keep the strokes loose.

While the wash is still wet, use the cotton cloth to wipe it back. Press firmly in the centre of the image and more lightly toward the edges, leaving more wash in the corners and in any recessed detail. The result should look uneven and slightly murky, not uniformly gray. Let dry completely, at least 90 minutes, before handling.