The simplest method is to remove the paint with a damp or tacky cloth. Clean the entire scissor and try to wipe away any loose rust. You are required to do it carefully, because you can cut your fingers.
Use a wire brush, if there are any difficult areas of rust. Move the brush back and forth to strip away rigid areas of debris. If your scissor is made of shiny metal, it is not one of the recommended methods for you. A wire brush may leave scratches on the scissor, and it will look really bad.
If the first two tricks don’t work, you need to go with a chemical paint stripper. Apply it thoroughly on the scissor with the help of the brushes. Let the chemical stay on the scissor for a few moments, and then hose off.
If the patches are too stubborn, you need to use sandpapers. Take a small piece of commercial metal 80-grit sandpaper, and rub the paint gently. After that, apply a light sanding to the scissor with a piece of 120-grit sandpaper. You can fold the sandpaper to reach the area right between the two arms of the scissor. Again, be really careful as the sandpaper may reduce the shine of the metal.
You need a sandblaster, if the paint is too hard to remove. These machines are easily available in the market and can also be rented. Blowing sand on the scissor will definitely remove the paint. It should be done by a professional though.
Once the entire paint is removed, wipe down the scissor with a damp cloth to get a clean surface.