I found oout from that frined what the "secret recipe" is.Its called
WHINK RUST REMOVER....it works flawlessy and quickly!!!
Just do not get any on your hands,or in your mouth and try not to get it on painted surfaces(it does contain Hydochloric Acid).All of which are no problem at all.It will make anyones windows like a mirror with very little effort and I am all about "very little effort".
I found it at Winn Dixie in the cleaning supplies section.
Here is there website.....
http://www.whink.com/rust_stain_remover.htm .....believe me you will thank me when you try it.
What I do is put gloves on (sometimes),put a little bit on a clean cloth and work in a small circular motion covering small areas at a time (4" by 4") and you will see the water stains disappear.Then I go over the area with Windex to clean up the resulting residue from all the hard water buildup being removed.
Your Welcome