The white film is just the salt residue, not a problem. Just put your hand in it and make sure all the salt is disolved. 24 hours should be fine and a few days is even better. The water is warm from just the pump running. In the summer my water is usually warmer than the tank water because I mix it in the garage for a whole week, but the chiller helps out when I put it in. If you do a wc every week you can just mix it all week then you will have your water ready to go when you do the next wc. It also helps when you have an emergency, you will always have water on hand to do a quick wc. And as always check your salinity.
Red Sea Reefer 300xl G2
Kessil AP9X