Digital BW, The Print

I've been playing with a can of PrintGuard spray, on Epson Archival
Matte and Hahnemulle [sic] William Turner.  I've noticed that it
*does* darken the blacks a bit, but also that it darkens the dark
grays a bit, the lighter grays a little bit, and the whites not at
all.  The end result is the midtones are a bit goofy.

How do folks handle this Are folks using customized
profiles/icq's/curves/... or are they adjusting the images themselves,
or?

g.