If pain is the problem guaifenesin is the answer. (Entex is phenylephrine + guaifenesin.) Generally anything with "tussin" in the name will contain it, as will most meds that are labeled as "non-drying sinus". It is also available in a strong OTC formula called Mucinex.

Guiafenesin is classed as an expectorant, so people tend to think that it is just cough medicine, but it is actually an antimucolytic. It works by thinning out mucous (any mucous that exists anywhere in the body). This means that it makes it possible for any muck that is in the sinuses to easily drain via the eustachian tubes. My ENT says that guaifenesin is the most effective OTC oral medication against sinus pain. (His top choice would be Rx steroid nasal sprays.)