The most popular method is to leave one side fastened and rolling the cover from the other side, turning it upside down as you go. This helps keep debris out of the spa when you go to put it back on. The main thing to remember is it is not going to act like a stiff foam cover. Keeping your chemicals balanced is better then shocking your spa water. Having your chlorine levels too high can cause damage to the vinyl.
Chlorine is hard on everyting it comes in contact with, spa covers, skin filters.
We Strongly recommend PristineBlue, non chlorine water treatment. Something to remember If your Spa Cap looks a little deflated after your kids use the spa it is probably due to the amount of water they managed to remove from the tub. I generally have to replace about 100 gallons of water for every four kids. Since the bottom of the cover rests on the water when the level is brought back to normal your cover should look just fine. In such cases I like to allow a couple days for the air inside to become constant before I place the snaps in the wood.