The two best ways to remove it would be with either our Super Cleaner or an IPA solution.
If using our Super Cleaner, you need to be careful with it, since it should not be used on glass.
If you're wondering what an IPA solution is, it's simply a mixture of isopropyl alcohol and water (google IPA solution for detailing).
Here is one article I've found for the ipa solution:
http://www.detailedimage.com/Ask-a-Pro/ask-a-pro-the-isopropyl-alcohol-ipa-wipedown/