I've chopped all my windshields and tried a lot of different methods. The easiest way is to take masking tape and run the tape across the shield to use for you line. That way you can always pull it back and change your arcs on your line over and over till you get it how you want it. Then use tin snips. I bought some from a hardware store for 9.99 (They were nicer ones)and they work awsome. You can run them right along the masking tape and it cuts a perfect edge just like sissors. Then when your done if you need to you can still take some sandpaper and clean up or reshape any edges if needed. I clean the inside of the winshield really good with soap and water, dry, and paint. I've always used whatever paint I could find and never had any problems. I'm sure the best paint is the paint everyone was talking about that is slightly flexible. I posted a thread about cobra windy's on my viper a couple days ago, if you go to it you'll see my end results.