dear qqkick, we have talked about this in another forum `push hand skills', maybe you want to take a look. Steel wrapped in silk or iron wrapped in cotton basically talked about the strength and power than hide inside the soft movements. The soft movements, relaxation 'sung' and non-resisting approach are the soft part, the cotton or silk, Yin element and the strength of the proper body structure, alignment, gravity, momentum, qi and yi mind intent)are the Yang element, the iron or steel. However, you need skills to be able to unite them together and arrive at the skills of like iron wrapped in cotton. The secret lies in your ability to `fang sung' (relax). However, sung is not the normal sense of relax with colappsed posture and dim mental stage. Sung is also discussed in our earlier forum. You must understand and internalized your ability to sung before you can grasp the internal power (neili) and use it as neijin.
You are right by relaxing into your posture but you have to make sure your `proper posture' is the correct one. You don't push by softening-up your posture, you push by been sung to allow all strengths to unite and become one and manifest at the palm or finger. Another word, you are moving your whole body mass as one unit without break hence, you are very strong. To understand the wonder of iron wrapped in cotton, you must comprehand what is sung and how it relates to internal strength.