When it comes to removing dried silly string, there are a few options available to you. You can either use a vacuum cleaner with the hose attachment, or a can of compressed air. Another option is to use a hairdryer on the lowest setting. Simply hold the hairdryer close to the silly string and wait for it to soften up and come off. Once it's softened up, you should be able to wipe it away with a paper towel or cloth.