Use Lip Balm to Protect Oddly Shaped Windows While Painting
Most of us use masking tape when painting around windows or window frames, and this works unless you have an unusual window or frame (like a round or round window). In this case, apply a thin layer of lip balm to the edges of the glass to let you paint freely and just wash off the excess.
You can simply rub it onto the glass surface, or use a cotton swab to apply the balm close to the edge of the glass. Extend the layer about half an inch from the edge to make sure it grabs as much paint as possible. When you’re ready to clean, simply wipe off the balm (and paint over it) with a dry paper towel. This method works well for irregularly shaped windows, but you can also use it for any window if you don’t have (or are out of) masking tape.
Window Painting: The Lip Balm Trick | Projection in my own style