I use razors.
If you are not comfortable using a razor that's ok.
Hard back razor blades work fine to remove just about anything on glass. I'd worry more about solvents getting on the paint, than the razor making scratches on the glass.
Tips:
- Always use a fresh blade. They only cost pennies in boxes of 100. Used blades may be nicked from hard use. Nicks cause scratches.
- Press the full width of the blade against the glass.
- Apply pressure at the center of the blade.
- Use a blade holder. It will allow shallower angels, a better grip and apply uniform pressure across the blade.
- The blade should slide smoothly along a clean surface.
- Hold it at about 30 degrees from the glass. More or less. Then angle used depends partly on what is being removed.
- Don't be tempted to use a corner.
- If the blade gums up with adhesive, where it will no longer slip across clean glass, get another. Scraper blades work by getting under the adhesive. Once the adhesive gets under the blade...
Blades and holders should be available at any Wal-mart or home center.
http://doityourself.com/store/6714471.htm
Edit: One place where you DON'T want a razor to get near, is the antenna printed on the inside of the windshield.