8 out of 10 times I love this stuff. But sometimes like on a black car it leaves a spotchy look like some of it got down in there good and some didnt. Am I doing something wrong? using too much or too little, waiting too long to wipe it off, not waiting long enough? I use the sponge pad it comes with. Or do some cars just not take to well to it as others do? I did another black car the same way and looked fantastic. When it happens I wax over it with another brand and it looks fine. Thanks