A few tips to remove all traces of paint from your windows

Warning! Never use paint thinner!
It can attack the glass, and even make it blurry or opaque.

For water-based paint (acrylic and vinyl):

1. Dampen a sponge with warm water.
   
2. Wipe the traces of paint.
   
3. Wait 20 seconds for the paint to become soaked with water.
   
4. Wipe clean with the sponge. The paint should be eliminated effortlessly.

For glycerophtalic or glycero paint:

1. Simply use a razor or box cutter blade.
   
2. Embed it in a cork stopper for a better grip and to avoid injuries.
   
3. Then, scrape the windows to lift the dry paint. You can also find window scrapers in hardware stores to use in the same way.