You can handle the matter either way, filing it yourself of using the services of the child support unit. It really depends on which method YOU prefer.
Doing it yourself - You would need to file the petition for an increase on your own and handle the litigation. Of course, if you can afford an attorney, the attorney can make the process much easier. This method would be more difficult, if you do it on your own, or more expensive, if you hire an attorney. However, it puts control of the matter in your hands and, as such, can lead to a better result.
Use child support services - They will handle the litigation for you, making the process easier. However, as you experienced last time, the control in hugely in their hands and the outcome may not be what you want.
So, if you are interested in the best possible result, consider doing it yourself. Conversely, if you are interested in making the process easier, consider using child support services.
Also, several customers have asked how they may direct a question to me in particular. If you specifically want me to assist you in your legal matter, just put "FOR JOSEPH" in the subject line and I will gladly pick up the question as soon as I am on-line.