I used the magnet pen on OPI Is That Silva?, a silver magnetic polish with holo glitters. It's very simple to use, just hold it over the wet magnetic polish and "draw" your pattern (I used a zig zag pattern) over the nail as close as you can without touching the polish. I first used it on a different polish and it didn't work, so I thought the pen just didn't do its job. But then I realised it was the polish that just didn't react to the magnet. With the OPI, it worked perfectly. You can get the pen here for 2.09$.
For more nail art items, check out Born Pretty Store (use the code below for a 10% discount)
The Magnet Pen was offered for reviewing purposes. Again, thank you very much, Born Pretty Store!