Raise your printers bed temperate to 60° via the LCD or through the Cura LE software.
Spray the PEI surface with the 50/50 mix of water/isopropyl alcohol and let sit for 30 seconds. This allows any oils/dust/debris/glue stick that may be on the bed to break down and dissolve into the water/alcohol mix.
Use the abrasive pad to scuff the surface of the PEI. This will open the PEI up and remove stuck on residue.
Use small circular motions in each direction on the bed.
Starting with an up and down pattern, followed by a side to side pattern, and finished with a diagonal patter.
Be mindful of the water/isopropyl alcohol mix.
Always keep the bed wet, but not saturated.
Spray more of the water mixture onto the build surface.
Wipe surface down with a cleaning cloth to remove the residue left by the cleaning/scuffing process.
You may need to spray and wipe down the PEI surface multiple times to ensure all residue is removed.
If you notice any water under the glass surface, remove the glass/PEI print surface (after it is cooled) and dry with a clean cloth.