I machine polished the windscreen today as it had historic wiper marks which were quite deep in places. I used 3M Glass Polishing Compound and Flexipads Rayon glass polishing discs. I worked a small area at a time (12 sections) and sprayed water occasionally to keep the screen cool. The result was far better than I had hoped for and I was really pleased with the result. The screen is now very clear and smooth. I further polished with a lighter polish and pad, added a sealant and replaced the wipers with new ones. Very pleased. 
