I know these can be done by thinning your polish with either polish thinner or acetone. I tried the thinner and it was a failure. I don't know if I added too much too fast or what happened. It was an "oil and water" type situation; the polish sort of curdled. Acetone it was! The only problem I had with the acetone was that it evaporates so darn fast. You'd better keep a little bowl of it handy while you do a mani like this. You have to dip your brush regularly.
This color scheme looked better in the bottles. It didn't translate as well on my nails. The colors I used are NYX Ink, Revlon Peachy and Jordana Chiffon; all over Sinful Colors Snow Me White and finished off with Poshé.
I like this technique and I'll definitely be trying it again.
On another note, can I just say how much I hate photographing my right hand! My nails and cuticles are always in worse shape than my left. It's harder to hold and use the camera with my left hand. My lighting source doesn't like my right hand near as much as my left. And to top it all off, the nail on my middle finger grows crooked. I try to shape my nail to compensate for it, but no matter what I do, the photos of my right hand will never measure up to my left hand. Ahhh... my vent is over now. I feel better. :)