Terry
Didny notice this one.
for the cement you need a scraper and a spray bottle so you can wet the window without rubbing it with your applicator.
Be sure to scrape in one direction only lifting off between scrapes, the reason is 2 fold.
1 .grit could get under your scaper on the backstrokes
2. by staying in one direction you know any scratches in opposite directions are not yours, point out any you find after the first window with an explaination how you scraped it, so they know you are not responsible, you should be ok because no-one cares about the way windows are treated these days(seems that way)
As for the yellowing , get a good quality cleaner available from window fitting firms, some use cif etc, or methylated spirit.
If using the last 2 do a test area first.
Hope this helps
Dave