Well I put it in a 5g bucket and run a water line to the bottom of the bucket and let the water run through it for a good hour. Then I mix it up and do it again. Even after several hours of rinsing it will still cloud your water up.
The thing about putting sand in an established tank is to do it slowly and in small amounts. I use a 12oz plastic cup and literally pour the sand in the areas I want it.
After I rinse it out as best I can I put SW
from my tank in the bucket so I'm not adding straight FW
to the tank. I scoop up a cup full and go to work. The trick is to lower the cup or bowl slowly let it fill with water and then slowly move it into position. When you are were you want tip the cup and begin pouring. If you do it this way you will have a minimal amount of cloudiness. Oh and turn off ALL of your flow when you do this.