I AM NOT A DOCTOR. (in case anyone gets uppity)
Sudafed, and associated drugs can have a powerful decongestant effect, but after several days use, can actually make the congestion worse if the underlying problem has not resolved (cold etc..). Many ENT people would advocate steam as the first point of call for sinusitis, it's very effective, and some would actively discourage the use of sudafed related treatments. As regards using saline, this actively overstimulates mucous production (its very powerful), that is its primary effect. Never before heard of it suggested to ease congestion!
I only know this as I have suffered from bad sinuses - steam was like a magic cure.