Hi Muneer
there is a free library on File Exchange that adds lots of parametrized parts to Multibody:
The simplest thing woul be to add this library and drag and drop the cylinder with hole block. You could take a look at how this was built as well. This library is provided by Steve Miller, our technical marketing manager for Simscape.
You don't see an hollow shaft with the method you posted about because there isn't one: there are two cylinder, one inside the other,so graphically you are going to see two cylinder even if one has negative mass. For the mathematical purpose though, it behaves like a hollow shaft. On the other hand the block in this library will be with a hole graphically.
Screenshot of the library and cylinder block:
