I've been doing this with plain water every morning. I have tried it with a drop of Grapefruit seed extract too. I've also done the same thing with collodial silver.
The ACV sounds like a good idea.
I have noticed that after a few flushes that even the plain water burns a bit. I think this has to do with the fact that the yeast is being cleaved from the sensitive tissue of the sinuses and leaves the sinuses a bit sore. I notice the burning the most at the very top of the sinuses, but it isn't too bad and I actually feel like I've accomplished something. My nose is a bit sore since I've been going this and as I wrote earlier, I've gotten some golden discharge in the morning.
Sinuses are getting much clearer though. I think it's working.