i have messed with it too. i think that the bit has to be ver y course, the dremel on high speed and if i swiped slowly it would leave a pretty bright spot. i also found out the more you go over the spot the duller it gets. i have a hard time getting the look to be consistent. but thinking about it, i maybe pressing too hard. i attached a picture one of my first attempts. the problem is findiing the bits that are course enough.