As you have already discovered, antibiotics don't work well for infections of the upper sinuses, and recent reports are that they don't really work at all.
Saline rinses don't work for upper sinuses, because of gravity, but the Flip Turn Sinus Flush defeats gravity, and as you'll see by the comments, it works
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, or you can kneel down and lean over a bathtub with the shower running.
As far as the antibiotics, once you start a round, you have to finish, but if you haven't started, a sinus flush will work better.