If your bird is sneezing and ejecting wet snot I personally would recommend a visit with an avian vet.
Birds will sneeze to remove irritants from their nares but they are generally dry sneezes, seeing how much mucous your bird has expelled I have to say I would be concerned it is possibly unwell or more than a bit of dust has irritated it, I have never seen that much wet stuff come out of a healthy bird.
@Mizzely