If you had sinusitis, then you probably still have sinusitis, just less noticeable except the post nasal drip. I'd recommend going to an ENT to see if and where your sinusitis is, or if you have another problem.
If you do have sinusitis, most likely in the upper sinuses, which may not cause congestion, then here is the most effective treatment
http://www.medhelp.org/user_journals/show/2322
The Flip-Turn Sinus Flush is mildly risky, because you have to bend over to do it, preferably in a shower, but you can also do it outside on soft ground.