Techniques, which include positions, movement and structure, can be used for defence, attack, or both at the same time. For example, a deflective move and a strike are often done together to fully take advantage of a situation, as simultaneous control and attack is better than just doing one thing after another.
Whatever the moves, techniques take time to understand and develop. As a matter of fact, as you delve into the concepts of techniques, the subtleties can be quite complex and difficult to refine, but once mastered you will appreciate that they are an eye opener for development of further techniques.
When new students are first shown a technique they can become put off since they find it hard and awkward to do, and give up before giving themselves a chance to cultivate their true potential. But the reason why they find it hard to grasp is down to the fact that their bodies are not used to the new type of movements they are being shown body motions that are unfamiliar and have as yet not been committed to muscle memory.
What they may not realise is, that to fully master techniques ultimately demands all the key elements to work effectively together, and this cannot be accomplished in a matter of weeks, it can take a life time to perfect. Nevertheless you would surprised us how quickly people improve through practice.
In other martial arts the component techniques can be are relatively longish sequences, in order to achieve a particular result (such as compliance), whereas in Wing Chun these are much shorter movement of a certain nature, that are not necessary going do much on their own. But as with all component techniques taught, in particular via Chi Sau training, these will be shown how to be applied in many different ways and with many other other combinations to achieve results.
It is through this on-going variety of practice that techniques improve rapidly as the body becomes more accustomed to required movements, at the same time the speed at which new techniques are grasped becomes significantly better.
Techniques are interdependent on the overall structure and moment of the entire body, which comes from stance and footwork practice. So the overall effectiveness is based on all of these improving.