Act quickly and wipe away the paint drip as soon as it appears using a damp cloth. When the paint is still wet, it is much easier to remove.
Warm some vinegar in a pan on the stove and apply to some cotton wool. Dab the affected area with the cotton wool and then scrape off with a new razor blade.
Mix water and dishwashing soap in a bucket so the liquid feels greasy. Apply to the affected area of the glass using a clean washing cloth. Scrape the area with a new razor blade to remove the paint. Clean the window with some glass cleaning solution and a squeegee.