In reality, Future works GREAT to increase clarity in windshields. I always leave them to dry (under cover) for a week....many modelers probably think that's longer than necessary - but that's what I do, and it works for me. I hate fingerprints.
Micro-Mesh also makes an amazing polishing kit for plastic and clear styrene. That's another option - and it's actually pretty cheap for what you get.
If your bus windows are foggy, you might need to go to another source because the Future might not work - cut your own windows from clear styrene or PETG (the same food grade plastic that drink bottles are made from). The stuff is great.
Good luck! And post pics of that bus!!!!!!