Just make sure that it really is a smear rather than just more dust. I say this because I got my own Arctic Butterfly not too long ago and tried using it to remove a couple of stubborn dust specs on my 5D sensor. The result looked horrible, and got worse each new time I tried, and I was convinced I had spread oil or grease over the sensor. I mean it looked really bad.
Eventually I realized that after each attempt the blotches were in a different place, so it was only dust I was moving around, and eventually I refined my technique to get the sensor completely clean. I don't know where all the dust was coming from but there was a lot of it.