Get some of the gallon freezer ziplocs bags, and pack the sand about 1/2 full in it. Squeeze out the air and zip it up. Lower into tank and unzip. Gently dump out sand - you'll kind of have to squeeze it out versus actually dumping it.
No matter what you do, if you're adding enough you'll eventually end up with a sandstorm. If worse comes to worse, you just work blind and rearrange in the morning when it all settles down.