Dusty Malt? Soak in water? Cloudy beer would be from proteins or bacteria maybe. What do you mean by dusty? All grain is "dusty" It's just normal, fine particles of husk and flour. If you are talking foreign debris dust, then just go buy fresh grain. It's cheap. Store it in a air-tight container. You don't want it exposed to the ambient conditions (especially long enough to get dusty). Soaking grains to clean them is pointless when you will be soaking them in the mash and vorlofing (filtering out small particles/clearing the wort). The whole process cleans the wort from natural particulates (dust). Dust is normal.
Here is what you want to focus on (Palmer
http://www.howtobrew.com/section4/chapter21-1.html ):
Symptom: The (finished) beer is hazy/cloudy.
Cause 1: Chill haze This is the number one cause of cloudy homebrew. It is caused by an insufficient cold break during cooling after the boil.
Cure: Use a wort chiller.
Cause 2: Starch If you made an all-grain beer and had incomplete conversion, or added/steeped a malt that needed to be mashed to an extract batch, then you can have residual starches in the beer that will cause cloudiness.
Cure: Watch the mash temperature and mash longer next time.
Cause 3: Yeast Yeast strains that have low flocculation, such as German Hefeweizen, will cause the beer to be cloudy.
Cure: Use a different yeast strain if you want a clearer beer.
In all cases, cloudiness can be combated by adding fining agents (e.g. isinglass, gelatin, Polyclar, bentonite) after fermentation. When all-grain brewing, the clarity can be enhanced by adding Irish Moss towards the end of the boil.
