In answering this question, the most important thing to remember is that too many literary techniques used all at once can often make the reader lose interest but this also means that the piece of text will lose meaning. Whilst you are trying to demonstrate your knowledge and the wide variety of techniques that you have learned, using a minimal amount of techniques correctly can push you into the higher band.
You would use literary techniques if you were trying to change the course of something, for instance, school uniforms. In this case, you would write a persuasive letter, explaining your side of the argument - whether you thought they were beneficial or a hindrance. You would scatter the literary techniques within your writing, for instance, listing in 3s, emotive language, and even wit or sarcasm to secure you into the higher band.