There is the possibility the glass is etched so there is no good way to fix that. I bought a bunch of used glass tanks and there are a couple that I cannot remove the cloudiness from. I have used every product listed above except for the pH Up. Also tried Muriatic Acid (Hydrochloric Acid 31.45%) with no improvement.
Even when filled with water, you can still see the cloudiness.
Just clean well and fill with water to see which side looks the best. Be sure any product you have used to clean the tank has been well rinsed out before setting the tank up for cycling.