As a person who's always had problems with allergies I've found that I experience lots of the goo needing to come out every dive. I have on occasions removed my mask at 20 or 30 feet and blew my nose, then cleared to watch the fish eat. They're fast buggers so you miss them most of the time, but if you time it right you'll see the fish snap it up. They love it.
I do not take any medicine while diving because my usual standby of Pseudofed can cause problems if you dive Nitrox, so now I'm back to the snot. Pseudofed did a lot to lesson that for me.
I never get nosebleeds, that's almost always a result of improper clearing or too fast of a descent or both. I've experienced it a few times with new buddies who are overweighted and drop like a lead brick. If I'm diving with a competent diver I never have problems with a bloody nose. So for the bloody nose people I'd suggest a very slow descent and start that clearing at the surface and at every breath on the way down. Don't force it, let it happen gently.
I can clear without any maneuvers if I go down slow enough, otherwise a gentle clearing works fine.
To summarize, I don't believe in using medicine due to my usage of Nitrox, but if you do get the 24 hour pseudofed only. Too much risk in the 4 hour versions. Take your time going down and clear gently. Don't clear on the way up.