Remove glue residue on basement wall

[Mattias_Jo1]

I've just removed an old weave from 2 walls that are against a drained exterior wall. Unfortunately, there are remnants of glue and presumably paint left. I've tried sanding it off with a regular hand sander. Tested with 120, 80, and 40 grit paper, but not a great method unless I have the wrong type of sandpaper. It can be scraped with a putty knife, but it would take forever. Any tips would be welcome.

 

[pelpet]

T-röd usually works well to remove glue.

 

[Mattias_Jo1]

Seems to be gypsum behind. Testing on a small area.