There's no real set number, but to make sure you can increase your use of techniques, it's a good idea to choose quotes that have a lot of scope to talk about, in terms of themes and character development. Make sure your quotes are lengthy enough (but not too long), and familiarise yourself with common language forms and features, like imagery and metaphor, which you can find online, or in things like Edible English.
Another good trick is to make sure that each new point you make is supported by evidence and analysis, which always must include a technique or two, or a comment about structure, tone or form of the text. You might have 2-3 points in a paragraph, and as long as each is supported by textual evidence, a technique, and analysis, you'll be fine. Remember, any good essay must show
how the composer manages to convey the main messages, or the themes of the text, which is where techniques come in.
Above all, let the question direct you as to how you might incorporate techniques into each point, as some questions may be more technique based than others. This is especially true of Extension English, because the emphasis is on your analysis of the text in relation to your module, rather than just quotes and techniques. Good luck!