My 2 cents:
I've been using irrigation for a short time now. I got a set of instructions from my doctor on this technique.
1. Keep your head level (dont look up or down)
2. Use an ear syringe and warm salt water
(point the syringe straight in toward the back
of your head, not up toward the brain)
3. Hold your breath and slowly squeeze a syringe full
of saltwater into each nostril alternately.
It should pass through your nose and fall onto
the back of your tongue. (dont swallow saltwater)
4. Do one to two cups a day
(with practice youll be able to increase the force
and amount of water through your nose)
(also, I find this procedure alot easier to do in
the shower as opposed to over the sink)
The water is supposed to fall onto the pallete but I've found that most of it just comes back out or it passes out the other nostril.
I've just recently tried adjusting how I hold my breath and in doing so have been able to get the solution to properly pass through the sinus tract onto the pallete.
It takes practice, but, if you hold your breath in the exhale position and relax a little (kind of like when we sometimes forget to breathe when were concentrating,
your not inhaling or exhaling or holding your breath, your just "not" breathing)you can get "alot" of salt water to pass through your nose into the back of your mouth. The trick is to do this without letting it reach your windpipe. (kind of tricky) Thats where the breath holding technique comes in. It takes some practice but its been "well worth" the effort for me. I'm not an expert on the topic, just passing on what is working for me. Hope this helps.
(lots of good info on the web for "nasal irrigation")