Pour 4 tbsp. of fabric softener into a spray bottle, and add warm water to fill the bottle. Shake the spray bottle to mix the solution.
Spray the wallpaper glue with the fabric softener solution, and allow it to sit for a few minutes. Use a ladder to reach higher places.
Apply the fabric softener solution using a paint roller if there's quite a bit of adhesive. Pour the solution into a paint tray, and dip the paint roller into your fabric softener solution, moving it back and forth to wet it completely. Hold the roller over the paint tray to allow excess solution to drip off. Apply the solution directly onto the wallpaper glue by rolling the paint roller back and forth over it. Allow the solution to sit on the adhesive for a few minutes. The fabric softener breaks down the wallpaper glue the same way commercial wallpaper removal products do.
Dip a clean sponge in a bucket filled with warm water. Wipe the area where the wallpaper glue has been removed. Rinse the sponge frequently to remove as much adhesive and fabric softener as possible.
Allow the wall to air dry.