I had spots the first time as well. I've found it works best if you soap again after you've soaped. That way you fill in all the holes and the water sheets off. Plus if you've missed something, you can get it with the sponge.
I've also noticed the black buildup on pads. My dad even thought that I had used the sponge to clean up the wheels and all the black was brake dust! Grrrrrr
LZ