I started working on my car using the pc and 3m smr with a yellow pad. I started with a white pad, but it was not getting out all the fine scratches so I moved up to a yellow pad. I am using a meguiars pad btw. My question is this: When the product would be virtually gone, it would start to leave a dusty residue, is this normal? I stoped working on the panel when the dust would appear and wiped it off with a mf towel. Is the dust just extra product that has dried? Or am I not using enough or maybe too much smr? I was using smr about the size of a quarter per section. It is a grey residue which makes me think it is smr, but does it sound like my technique is ok?