At this point, you've mastered the basics of justifying your incompetence, but you're looking to take your skills to the next level. Congratulations! Here are some more advanced techniques to help you do just that.
When faced with a task, respond with a vague description of your intentions, rather than a clear plan of action. This will buy you time, and possibly even make you appear competent.
Read more about The Art of the Vagueness
When someone asks you to do something, quickly shift the topic to something else. This is especially effective if you're being asked to do something you can't do, or don't want to do. Just say 'oh look, have you seen this?' and point to a shiny object.
Read more about The Power of the Redirect
When faced with a task, start talking about something completely unrelated, but in a way that makes it seem like it's still relevant. This will confuse and disarm your opponent, giving you time to come up with a real plan.