The first time my daughter had croup I was worried. It sounds very scary. The younger a child is, the more croup affects them because it causes the larynx and trachea to swell. Thus, their airflow is restricted and vibrates, creating the barking sound I've become too familiar with. The younger the child, the smaller their air pipe and the more serious their croup sounds/is because the inflammation of their larynx and trachea will take up more space.
In the rare case that their air flow becomes too restricted, steroids are used to reduce inflammation and allow normal breathing.
Croup is *usually, usually, usually* caused by a respiratory virus. Antibiotics only have an affect on bacterial infections; they will not treat a viral infection. A viral infection must run its course.
Just as an aside: Was it determined that your son's croup was bacterial? Was there an emergency reason for the steroids? (not an attack, just wondering...)
I've treated my daughters croup in the following ways:
For fever: Tylenol and/or Ibuprofen depending on how high the fever was.
For cough: Lavender/licorice root infused honey.
For comfort and for cough: A bath with a few drops of eucalyptus oil (I've left the room steamy before she goes in. At our house we only have a shower, so I've done the same but with a shower.) I also make herbal teas, sweetened with honey (we are not lactose intolerant so we don't get phlegmy with milk) and cooled down with milk.
The cough gets worse when the child is upset (a natural reaction to being scared and sick) so I try to keep her as calm as possible. Holding her, rocking her, letting her sleep next to me, etc.
Good luck!