I just redid a 5 gl tank and I used brightwell aqua soil. Now every time I put a plant in the substrate a fine layer of dust kicks up. Will this dust eventually go away or will it always be there? I tried rinsing it before I placed it in but that did no good.
If the product is anything like ADA Aquasoil, then the dust is a result of the soil particles falling apart. In this case, then no, it will not go away unless you physically remove it. I simply think this is a characteristic of all soil-based substrates; they eventually disintegrate into soil particles (i.e. dust).
I don't know anything about Brightwell's substrate. Other clay-based and soil-based substrates often have fine particles that are easily disturbed in new tanks.
But, it gets better over time! As the biofilm develops, the fine particles become bound together and settle out of the water column more quickly. Mature soil-based tanks often clear surprisingly fast after even a major disurbance.
Fine dust 
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