Colistin has been useful for me!
Colisitin has helped me a lot over the years, especially when I feel a cold coming on or after traveling & I'm congested. I do it every other month & haven't had any side effects besides a little sticky mouth at night when I go to sleep. After I mix it with the sterile water I wait about 10 minutes before I use it. One mixed solution can last about 24 hours, so if you don't do the 2 doses within 24 hours throw it out. Also when you are mixing the sterile water into the medication, try and push the water into the vial slowly, to create less bubbles, don't just push it in quickly.
I've found Colistin to be much more tolerable than Tobi & takes a lot less time. Good luck!