The idea was to try and smear charcoal to blur like the view through the cocktail glass. Unfortunately it didn’t really smear well and then I added some loose charcoal powder which stuck in the damp glue and gave some interesting detail when I tried to smear it, but not the blurry smear I was after.
So this technique might be useful in drawing for creating a rough texture but it didn’t work for this image. Possibly using a rewettable medium and then smearing water over it might work.
Incidentally don’t iron paper with damp glue even using a protective cloth. You can see the resultant delamination of the paper above.