Digital BW, The Print

You know, after I posted that this method of spotting was clever, I
started thinking (I know, sometimes a bad idea). Glossy paper prints
very differently than the non-OBA matte paper I use, with very different
shades. It seems like it would be very easy to pick the wrong grey scale
step for spotting, because when I spot the matte paper, it will be a
different shade. I guess you would learn over time which of the steps on
a given type of glossy paper matched the actual shade of the hole you
needed to fill on a given matte paper, but it seems like this would be a
pain.

Perhaps it doesn't matter in practice; I haven't tried it yet.

Andrew