Like I said in my post, try adding Tree Tea Oil to the mixture.  TTO is like sticking menthol in your nose - I find it keeps the air passages open much longer than just a regular flush and it kills bacteria as well.  There are different qualities of TTO so I'd suggest starting with just one or two drops - I'm at about 5 or 6 but the kind I use is not as strong as I've had before.  You'd be amazed at how it opens up the airways.

I think you mentioned before that you create a saline solution similar to what I posted - 1 teaspoon of sea salt and 1/2 teaspoon of soda per cup of water.  Make sure it is thoroughly mixed in body temperature water.  (There are different instructions at the site below.)  I have found that to be easy on the sinus passages.  I have two irrigators, the Neti pot and a plunger.  Have never even used the plunger because it appears too harsh and am afraid I'll use too much pressure.  There is also an irrigator that attaches to a Water-Pik cleaner but again am afraid that it will create too much pressure.  The Neti pot allows a natural flow through the sinuses.

Here is a site that gives instruction on the use of a Neti pot and their saline solution is not as strong as what I mentioned above - and they use table salt.

http://www.neti-pot.com/how-to-use-a-neti-pot.cfm?googlead-neti%20pot%20instr...

Here's a site that talks about oils including Tea Tree Oil for use with a Neti pot.  It says to use only one drop of TTO and that's what I started with.  I originally had a very good oil and worked my way up to three drops, then bought a lower grade TTO and currently use 5 - 6 drops.  I find that the TTO keeps the passages clear for quite a while after the irrigation.  This site also mentions other oils including eucalyptus - after using the Neti pot.  There is a steam bath at Bally's where I go once in a while and they have a sprayer of eucalyptus oil there and it really clears out the sinuses.

http://www.ehow.com/facts_5593374_essential-pot-treat-sinus-infections.html

Hope this helps.