Can I use this primer on interior vinyl window frames that have been properly cleaned and sanded? If not, what do you recommend?

Hello, Thanks for your interest in our Kilz Premium Primer! If you're going to sand and clean the vinyl siding before priming, then you'll be good to go. This primer can be applied directly over vinyl surfaces without having to worry about the adhesion. If you'd like, feel free to reach out directly to our Customer Care Department if you have any other questions or concerns. I hope you have a good rest of your day, and best of luck with your project - Vince