If you don't get results with a neti or Neilmed, then it's probably lodged in your upper sinuses, and you'll be fighting gravity, and gravity always wins. The Sinus Flush uses gravity to get saline where it needs to go,and hopefully wash out the allergens.
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.