A few years back Marshall Rusman (?) up in Canada posted to the list on
how to clean glass really nice and easy using 00000 steel wool-the finer
the better.
I tried it and it worked well to remove
 bugs , water spots, tar, & road grime.
Now here's another spin on the process.
I apply Rain -X to the wool as I'm cleaning
the glass .
It adds a lubricant to the wool to assure me that there isn't any
scratching of the glass.
I go back and wipe the glass down with a turkish towel after this
application, and I've killed two birds with one stone.
( This is just a figure of speech for you animal rights, and bird loving
folks out there )
There has not been any damage to any of my glass, no scratching anyway.
Bon Ami is a good product too, but much too time consuming for me.

RC