I updated my recent article on how to vacuum clean your camera (or other gear). I also added there this old trick, which I have used ever since I managed to ruin one camera because of the fine dust.

Obviously this may not keep the camera entirely dust free, since I just had to do that vacuum clean trick for my Canon G5x. But without such plastic bag protection, the situation could be much worse. Besides, one can even use such small plastic bag as a "mini umbrella" above the camera, if it is raining.

The point is that there are so much small fabric dust inside overcoat pockets, that it may eventually even cause a short-circuit on the camera electronics. That is what once happened to me. And if that happens, then a quick overall vacuum cleaning may not be enough.