[burr740]

I would just use it.

+1

A little oily film is normal and it doesnt really transfer to the tank as long as you rinse it well.

For me it takes 4-5 rinsings, and it's easier if you dont try to do too much at one time. In a 5 gal bucket I fill about 1/4 the way up with sand. Add water til the bucket is 75% full or so, and stir the crap out of it. Pour off the excess water and repeat 4-5 times until the water becomes mostly clear.

Then dont worry about it.