You may try a nasal spray made of borax, water and a drop or two of Iodine OR a drop or two of H202 3%
-or in the neti pot of course.
This was quite successful in one sinus case I know of. You will have to find out the ratio of each, borax in water is very soothing and has a saturation point on 4,5 %, it is cleansing and takes care of both bacterias and fungus. (Sinusites can be fungal)