I think anything but water would dissolve it, and cause it to migrate further into the surface. Am I wrong?
I would use water, patience, time, a plastic 2" drywall knife, and an attitude.
The attitude is to get as much as you can, float the wall to get a fresh surface, retexture, and paint.
At least, that's what I would do.
You can do less, but you will get less.
Steve