DS had a lot of sinus issues until he was about 1 1/2. We used saline spray, the dreaded booger sucker. And I also would steam up the bathroom really good -- keep the door closed after DH would take one of his marathon showers and then I'd get a bath ready for DS. I'd give him baths in the morning and right before bed, which seemed to get the stuff moving.
We use simply saline -- compressed air (aerosol) spray instead of regular saline spray. Noticed a bit of a nasty backwash effect when I'd spray the regular stuff in his nose and figure it can't be good to have that stuff sitting in the bottle. Bleah!
We'd asked about nasal spray decongestants once, just to get him over a particularly nasty head cold and were told by his doctor absolutely not.
On a side note. Is the nasal mucus normal (clear) in color? Or is it yellow and looks like a sinus infection. We found that we were dealing with a nasty sinus infection that never quite went away. DS's doctor finally prescribed augmentin for 20 days to get rid of it