Your ENT is halfway correct--a nasal rinse will cure the problem, except due to gravity, the nasal rinse will only go about halfway up your sinuses, and will be nearly useless. The smell is caused by anaerobic bacteria, near your olfactories.
I developed the flip-turn sinus flush, which has cured 4 bouts with the smell (like Parmesan and dogpoop) which I'd get when I had chronic sinus problems (now permanently cured). The drawback is that you have to bend over in a shower to take advantage of gravity, and that's always a risk. If you want the technique, cursor the blue "friggy" and go the the Journal. The instructions seem complicated, but that's a result of caution.
You can also look for also try a Grossman nasal pulse machine, which operates on the same theory. I've never tried it, though.
i have the same effing thing!!!!!
message me if u find out how to get rid of it