The only reason to rinse it is to avoid a long duration of cloudiness in the tank. Nothing will hurt the tank if it goes unrinsed, but I still recommend a good rinse.
The way I do it is in a small bucket, half full with sand, and run water into the bucket until it fills. stir it/ sift it under the water with your hand, pour of the water and repeat till it clears. Usually takes 3-4 times, then empty and get more new sand in the bucket and have at 'er once again.
I would agree with austinsdad on about 30-40 minutes for a 40# bag. Some would say that's a waste of time.... others hate a cloudy tank. My tank never clouded after rinsing my aragonite in the described way.