There are other felting tools which hold more needles than this, such as the Colonial Needle Felting Tool. While you will be able to felt a large area quickly with this tool, I find that it is not as easy to manipulate as the Clover tool.

For detail you should use a 40 triangle. I generally just hold the needle in my hand, but you can also use a tool as well. The clover pen allows you to remove all but one of the needles, so that you can do the finer detailed work in comfort.

As you felt more, you will notice the difference between using the various needle gauges in your work. If you are noticing that there are very apparent needle holes on the surface of your work, try switching to a more detail-oriented needle.