Okay, so this is gonna sound a bit wierd, but I'm sure it contributed to my sinuses clearing up! (I used to often have sinus issues and wouls have to abort dives because of nosebleeds and pain - especially from frontal sinus).
Anyway, whenever i was a bit 'clogged up' and knew I would be diving in the next few days, I would visualize my sinuses being perfectly clear and clean - like a great, big, airy, space, full of fresh, flowing air (sometimes I'd picture that my sinus cavities and channels were a big beach scene on a warm day, with moist, but fresh, flowing sunny air going through them).
Whenever my sinuses were on my mind, I pictured the above. I definitely think it contributed to clear sinuses, and would suggest you try it - as unconventional as it is!
