You don't have to wait that long as long as it's dry, it's safer to wait but I put it on my wife's phone and my own and accidentally hit the power button while applying and all was well.
I have just the shield on mine and I love it, it's in my pocket all day and so far so good. My wife has a pink rubberized case for it so it looks more girly, I found that once you have the shield on, if you bought the full body one, it makes it much easier to grip, also in my Nissan Quest van I have the faux wood panels on the dash and such and the invisible shield grips it great so I can set the phone on the dash and use it to read texts or see what's playing without picking it up or taking my eyes off the road for too long.
HTH
D