Interesting idea. Getting a sense of how to hold the razor and touch it to your skin. Add some lather and you can get an idea of how you're missing spots in curves, etc. An alternative that's been posted is to use a shavette razor with a plastic/paper insert made from a business card, etc. Either way will help you figure out how to position your arms, turn your wrists, and handle the razor in a way that is comfortable and allows you to see while lowering the chance that you'll slice your face.

Thanks for posting!