The effects are not on the brushes, the preview is just an example of what kind of effects you can achieve with them. I left them plain because I figured you could customize them to your liking.
If you want to achieve similar effects like in the preview you simply go to your "other dynamics" or "transfer" tab and adjust the opacity option to pen pressure, you can also go to the scatter tab and do the same and create all sorts of super awesome effects
Enjoy! XD
and please link back to my blog or to my DA account if you use them