Yes, works well as long as it's a painted headstock and you can get thin enough sheet so there's not a ridiculous amount of paint to build up, or too thin so there's no depth to the colour. Also, don't draw any positioning lines that you will probably be able to see once you've sanded the shell! I may even spray a white coat first and glue the sheet on top of that - though with some colours of shell they recommend a dark background to help bring out the colour.