Ok, I just learned this technique about 2 days ago, but WOW am I impressed with it! Very easy to get a marble like look. It definitely looks different from a water marble but still fun. Rather easy to do and quicker than I thought it would be as well.
See how easy after the jump...
Pick 2 or 3 colors for your marble. From the colors you've chosen for your marble, choose the lightest color and paint your nails with that. This is in case you miss a spot, no bare nail will show through.
On the plastic drop a couple drops of each of your colors. Don't drop the colors on top of each other or the colors will mix and you won't get much in the way of swirls of color.
Fold the plastic over and poke at the drops. Swirl them a bit. Again, not too much or you'll just mix the colors together, not marble them.
Open up the plastic and you'll have an inkblot looking thing. find a good spot and dip your nail into it. I don't have a picture of that because I needed both hands to do it and juggling the camera just wasn't working. Make sure to press the paint into the sides of your nails too. Any bare spots can either be marbled over the top of again, or touched up with a bit of extra paint. Be forwarned, this can get a little messy and you will likely get paint all over your hand. Just keep your remover on hand to clean up the mess. If you really hate that kind of mess you can pre-tape your hand like you do for water marbles. I thought that just slowed me down though. You can get 2 or 3 nails dipped off one sheet of plastic before it dries, but I do recommend using clean plastic when the paint dries. I couldn't get the paint to peel off the plastic and got dry flakes of paint sticking to my nails. The grand part of plastic wrap marbling is you can redo nails over and over without having to remove the polish that didn't look right. Just redip them when they dry. I redid 3 nails because I didn't like that they turned out so much darker than the others.