I followed these instructions at Design Mom just used up two old nail varnishes i had lying around and some cartridge paper.
This is my favourite two tone one, love the big swirl of pink :)
And this is my fav one tone one, it hasnt come out very well in the photo but it has a wonderful subtle marble pattern
I did have some fails though - as Design Mom mentions you have to act quickly or the nail varnish dries - leaving bug chunks like on this one :(
But sometimes it just make a more patchy pattern like this one, which i quite like!
I love this technique, im definitely going to try it again, maybe with some bolder colours next time...