Not a doctor, not going to pretend to be one, but am prone to congestion from a combination of flying/allergies/air quality. For me, the difference between a good dive trip and a bad one is going in with clear sinuses.
Not sure if you've looked into either, but for me, long term use of generic flonase (fluticasone priprionate) every evening in the weeks leading up to a dive trip and during, and short term use of generic afrin (oxymetazoline hcl) the mornings of dives up to three days in a row really makes a difference, much easier equalization, and much less congestion after the dive and no mild barotrauma. I take the fourth day off usually, let the afrin blowback run its course with a 1-2 day SI (Beer and tequila day!) And then can do 3 more days of clean diving.
Near as I can tell, both are relatively safe and not as big of a risk of wearing out on a dive causing a reverse block as oral decongestants like psuedoephedrine.