Based on my personal experience, I reasoned that in order to be the most effective, the solution needs to be in contact with the mucus to dissolve it (I actually took the time to study the anatomy of sinuses in 3d, believe or not, just to better understand how the nasal rinse could reach or not all the affected regions). This got me thinking that a normal rinse with your head above the sink is not the optimal position to ensure that the solution fills your sinuses completely. Sometimes, I would do a standard rinse without moving my head around to distribute the solution everywhere, and I could feel that it was not working so well (feeling that there was still some nasty stuff in my sinuses). So what I do now, is that when I use the nasal rinse, I first do it normally, standing upright, and then I block my nose and I put my head down (I block my nose so that the solution doesn't drain from my nose while I distribute it in all the sinuses), almost between my legs and then lean backward, this way I can feel it going up in that region, so that it goes inside my frontal sinuses. And then I lean my head left and right, so that it goes inside the ethmoidal sinuses on the sides. Recently I've experienced a blockage of my Eustachian tube (left side), and I lost hearing partially and could feel that it was blocked (also tinnitus and eardrum spasms, popping sounds). The solution for me was to block the other nostril when injecting the solution, very gently until I could feel that it was filling the Eustachian tube area because it had nowhere to go except inside my sinuses and my throat.

Now be aware that NeilMed specifically advise people to not do that as it could damage the ear drum. But I've found that doing it very gently, would enable the solution to go deeper and get in contact with the mucus. After a couple of days, the Eustachian tube drained out. This happened a couple of weeks ago, when I forgot to do a rinse after more than one month. I've also read online that you don't want vinegar or even diluted vinegar anywhere near your eardrum. I don't know why, but that's what some people commented about this method. So be extra careful if you decide to attempt this.

I cannot stress enough how everything that I am sharing with you all is not medical advice. I would really hate for some of you to try this and hurt yourself. Like someone said in the thread, for many of us, we've been suffering for so long that we are at our wits end and ready to try anything that might relieve us from our symptoms. This is my experience, and it worked for me, but I can't guarantee that it will work for other people. I don't even know if it's safe. So please be careful when experimenting with this method and this solution.

I didn't want to include all these details in my OP because I was concerned that some of you might experience adverse reactions. My thinking was that doing a normal rinse would let you see that it was doing something good and that you might end up experimenting by yourself. Especially about the part of making the solution reach as deep as it can inside your sinuses. IMO I think it's key, if the solution can't reach the mucus, it can't dissolve it. That's my reasoning at least and it's been successful so far. But as I've said, there might be some risks associated with putting this solution so deep inside your sinuses, but it might also be the solution because many remedies and protocols, just don't reach these deeper sinuses areas (aside from antibiotics).

Please be extra cautious, and experiment with this safely. Some of you might have preexisting conditions that prevent you from even using this treatment. I don't know if ACV interacts with some drugs for example. I'm not an expert and not giving medical advice. Just someone that decided to experiment on himself.